Commit Graph

297 Commits

Author SHA1 Message Date
Miklos Szeredi
6266d465bd ovl: don't fail copy-up if upper doesn't support xattr
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-18 16:11:24 +02:00
Amir Goldstein
82b749b2c6 ovl: check on mount time if upper fs supports setting xattr
xattr are needed by overlayfs for setting opaque dir, redirect dir
and copy up origin.

Check at mount time by trying to set the overlay.opaque xattr on the
workdir and if that fails issue a warning message.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-18 16:11:24 +02:00
Amir Goldstein
8137ae26d2 ovl: fix creds leak in copy up error path
Fixes: 42f269b925 ("ovl: rearrange code in ovl_copy_up_locked()")
Cc: <stable@vger.kernel.org> # v4.11
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-18 16:11:24 +02:00
Arnd Bergmann
72d42504bd ovl: select EXPORTFS
We get a link error when EXPORTFS is not enabled:

ERROR: "exportfs_encode_fh" [fs/overlayfs/overlay.ko] undefined!
ERROR: "exportfs_decode_fh" [fs/overlayfs/overlay.ko] undefined!

This adds a Kconfig 'select' statement for overlayfs, the same way that
it is done for the other users of exportfs.

Fixes: 3a1e819b4e ("ovl: store file handle of lower inode on copy up")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-15 10:53:07 +02:00
Linus Torvalds
b948abf53a Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs update from Miklos Szeredi:
 "The biggest part of this is making st_dev/st_ino on the overlay behave
  like a normal filesystem (i.e. st_ino doesn't change on copy up,
  st_dev is the same for all files and directories). Currently this only
  works if all layers are on the same filesystem, but future work will
  move the general case towards more sane behavior.

  There are also miscellaneous fixes, including fixes to handling
  append-only files. There's a small change in the VFS, but that only
  has an effect on overlayfs, since otherwise file->f_path.dentry->inode
  and file_inode(file) are always the same"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: update documentation w.r.t. constant inode numbers
  ovl: persistent inode numbers for upper hardlinks
  ovl: merge getattr for dir and nondir
  ovl: constant st_ino/st_dev across copy up
  ovl: persistent inode number for directories
  ovl: set the ORIGIN type flag
  ovl: lookup non-dir copy-up-origin by file handle
  ovl: use an auxiliary var for overlay root entry
  ovl: store file handle of lower inode on copy up
  ovl: check if all layers are on the same fs
  ovl: do not set overlay.opaque on non-dir create
  ovl: check IS_APPEND() on real upper inode
  vfs: ftruncate check IS_APPEND() on real upper inode
  ovl: Use designated initializers
  ovl: lockdep annotate of nested stacked overlayfs inode lock
2017-05-10 09:03:48 -07:00
Amir Goldstein
5b6c9053fb ovl: persistent inode numbers for upper hardlinks
An upper type non directory dentry that is a copy up target
should have a reference to its lower copy up origin.

There are three ways for an upper type dentry to be instantiated:
1. A lower type dentry that is being copied up
2. An entry that is found in upper dir by ovl_lookup()
3. A negative dentry is hardlinked to an upper type dentry

In the first case, the lower reference is set before copy up.
In the second case, the lower reference is found by ovl_lookup().
In the last case of hardlinked upper dentry, it is not easy to
update the lower reference of the negative dentry.  Instead,
drop the newly hardlinked negative dentry from dcache and let
the next access call ovl_lookup() to find its lower reference.

This makes sure that the inode number reported by stat(2) after
the hardlink is created is the same inode number that will be
reported by stat(2) after mount cycle, which is the inode number
of the lower copy up origin of the hardlink source.

NOTE that this does not fix breaking of lower hardlinks on copy
up, but only fixes the case of lower nlink == 1, whose upper copy
up inode is hardlinked in upper dir.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Miklos Szeredi
5b712091a3 ovl: merge getattr for dir and nondir
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Amir Goldstein
72b608f085 ovl: constant st_ino/st_dev across copy up
When all layers are on the same underlying filesystem, let stat(2) return
st_dev/st_ino values of the copy up origin inode if it is known.

This results in constant st_ino/st_dev representation of files in an
overlay mount before and after copy up.

When the underlying filesystem support NFS exportfs, the result is also
persistent st_ino/st_dev representation before and after mount cycle.

Lower hardlinks are broken on copy up to different upper files, so we
cannot use the lower origin st_ino for those different files, even for the
same fs case.

When all overlay layers are on the same fs, use overlay st_dev for non-dirs
to get the correct result from du -x.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Amir Goldstein
b7a807dc20 ovl: persistent inode number for directories
stat(2) on overlay directories reports the overlay temp inode
number, which is constant across copy up, but is not persistent.

When all layers are on the same fs, report the copy up origin inode
number for directories.

This inode number is persistent, unique across the overlay mount and
constant across copy up.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Amir Goldstein
595485033d ovl: set the ORIGIN type flag
For directory entries, non zero oe->numlower implies OVL_TYPE_MERGE.
Define a new type flag OVL_TYPE_ORIGIN to indicate that an entry holds a
reference to its lower copy up origin.

For directory entries ORIGIN := MERGE && UPPER. For non-dir entries ORIGIN
means that a lower type dentry has been recently copied up or that we were
able to find the copy up origin from overlay.origin xattr.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Amir Goldstein
a9d019573e ovl: lookup non-dir copy-up-origin by file handle
If overlay.origin xattr is found on a non-dir upper inode try to get lower
dentry by calling exportfs_decode_fh().

On failure to lookup by file handle to lower layer, do not lookup the copy
up origin by name, because the lower found by name could be another file in
case the upper file was renamed.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Amir Goldstein
c22205d058 ovl: use an auxiliary var for overlay root entry
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Amir Goldstein
3a1e819b4e ovl: store file handle of lower inode on copy up
Sometimes it is interesting to know if an upper file is pure upper or a
copy up target, and if it is a copy up target, it may be interesting to
find the copy up origin.

This will be used to preserve lower inode numbers across copy up.

Store the lower inode file handle in upper inode extended attribute
overlay.origin on copy up to use it later for these cases.  Store the lower
filesystem uuid along side the file handle, so we can validate that we are
looking for the origin file in the original fs.

If lower fs does not support NFS export ops store a zero sized xattr so we
can always use the overlay.origin xattr to distinguish between a copy up
and a pure upper inode.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:58 +02:00
Amir Goldstein
7bcd74b98d ovl: check if all layers are on the same fs
Some features can only work when all layers are on the same fs.  Test this
condition during mount time, so features can check them later.

Add helper ovl_same_sb() to return the common super block in case all
layers are on the same fs.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-05-05 11:38:57 +02:00
Amir Goldstein
4a99f3c83d ovl: do not set overlay.opaque on non-dir create
The optimization for opaque dir create was wrongly being applied
also to non-dir create.

Fixes: 97c684cc91 ("ovl: create directories inside merged parent opaque")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org> # v4.10
2017-04-26 14:33:44 +02:00
Amir Goldstein
b0990fbbbd ovl: check IS_APPEND() on real upper inode
For overlay file open, check IS_APPEND() on the real upper inode
inside d_real(), because the overlay inode does not have the
S_APPEND flag and IS_APPEND() can only be checked at open time.

Note that because overlayfs does not copy up the chattr inode flags
(i.e. S_APPEND, S_IMMUTABLE), the IS_APPEND() check is only relevant
for upper inodes that were set with chattr +a and not to lower
inodes that had chattr +a before copy up.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-04-20 16:37:26 +02:00
Kees Cook
33006cdf9c ovl: Use designated initializers
Prepare to mark sensitive kernel structures for randomization by making
sure they're using designated initializers. These were identified during
allyesconfig builds of x86, arm, and arm64, with most initializer fixes
extracted from grsecurity.

For these cases, use { }, which will be zero-filled, instead of
undesignated NULLs.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-04-20 16:37:26 +02:00
Linus Torvalds
04bb94b13c overlayfs: remove now unnecessary header file include
This removes the extra include header file that was added in commit
e58bc92783 "Pull overlayfs updates from Miklos Szeredi" now that it
is no longer needed.

There are probably other such includes that got added during the
scheduler header splitup series, but this is the one that annoyed me
personally and I know about.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-03-08 10:42:13 -08:00
Amir Goldstein
b1eaa950f7 ovl: lockdep annotate of nested stacked overlayfs inode lock
An overlayfs instance can be the lower layer of another overlayfs
instance. This setup triggers a lockdep splat of possible recursive
locking of sb->s_type->i_mutex_key in iterate_dir(). Trimmed snip:

 [ INFO: possible recursive locking detected ]
 bash/2468 is trying to acquire lock:
  &sb->s_type->i_mutex_key#14, at: iterate_dir+0x7d/0x15c
 but task is already holding lock:
  &sb->s_type->i_mutex_key#14, at: iterate_dir+0x7d/0x15c

One problem observed with this splat is that ovl_new_inode()
does not call lockdep_annotate_inode_mutex_key() to annotate
the dir inode lock as &sb->s_type->i_mutex_dir_key like other
fs do.

The other problem is that the 2 nested levels of overlayfs inode
lock are annotated using the same key, which is the cause of the
false positive lockdep warning.

Fix this by annotating overlayfs inode lock in ovl_fill_inode()
according to stack level of the super block instance and use
different key for dir vs. non-dir like other fs do.

Here is an edited snip from /proc/lockdep_chains after
iterate_dir() of nested overlayfs:

 [...] &ovl_i_mutex_dir_key[depth]   (stack_depth=2)
 [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
 [...] &type->i_mutex_dir_key        (stack_depth=0)

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-03-08 15:05:23 +01:00
Linus Torvalds
e58bc92783 Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs updates from Miklos Szeredi:
 "Because copy up can take a long time, serialized copy ups could be a
  big performance bottleneck. This update allows concurrent copy up of
  regular files eliminating this potential problem.

  There are also minor fixes"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: drop CAP_SYS_RESOURCE from saved mounter's credentials
  ovl: properly implement sync_filesystem()
  ovl: concurrent copy up of regular files
  ovl: introduce copy up waitqueue
  ovl: copy up regular file using O_TMPFILE
  ovl: rearrange code in ovl_copy_up_locked()
  ovl: check if upperdir fs supports O_TMPFILE
2017-03-03 12:02:42 -08:00
Linus Torvalds
590dce2d49 Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs 'statx()' update from Al Viro.

This adds the new extended stat() interface that internally subsumes our
previous stat interfaces, and allows user mode to specify in more detail
what kind of information it wants.

It also allows for some explicit synchronization information to be
passed to the filesystem, which can be relevant for network filesystems:
is the cached value ok, or do you need open/close consistency, or what?

From David Howells.

Andreas Dilger points out that the first version of the extended statx
interface was posted June 29, 2010:

    https://www.spinics.net/lists/linux-fsdevel/msg33831.html

* 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  statx: Add a system call to make enhanced file info available
2017-03-03 11:38:56 -08:00
David Howells
a528d35e8b statx: Add a system call to make enhanced file info available
Add a system call to make extended file information available, including
file creation and some attribute flags where available through the
underlying filesystem.

The getattr inode operation is altered to take two additional arguments: a
u32 request_mask and an unsigned int flags that indicate the
synchronisation mode.  This change is propagated to the vfs_getattr*()
function.

Functions like vfs_stat() are now inline wrappers around new functions
vfs_statx() and vfs_statx_fd() to reduce stack usage.

========
OVERVIEW
========

The idea was initially proposed as a set of xattrs that could be retrieved
with getxattr(), but the general preference proved to be for a new syscall
with an extended stat structure.

A number of requests were gathered for features to be included.  The
following have been included:

 (1) Make the fields a consistent size on all arches and make them large.

 (2) Spare space, request flags and information flags are provided for
     future expansion.

 (3) Better support for the y2038 problem [Arnd Bergmann] (tv_sec is an
     __s64).

 (4) Creation time: The SMB protocol carries the creation time, which could
     be exported by Samba, which will in turn help CIFS make use of
     FS-Cache as that can be used for coherency data (stx_btime).

     This is also specified in NFSv4 as a recommended attribute and could
     be exported by NFSD [Steve French].

 (5) Lightweight stat: Ask for just those details of interest, and allow a
     netfs (such as NFS) to approximate anything not of interest, possibly
     without going to the server [Trond Myklebust, Ulrich Drepper, Andreas
     Dilger] (AT_STATX_DONT_SYNC).

 (6) Heavyweight stat: Force a netfs to go to the server, even if it thinks
     its cached attributes are up to date [Trond Myklebust]
     (AT_STATX_FORCE_SYNC).

And the following have been left out for future extension:

 (7) Data version number: Could be used by userspace NFS servers [Aneesh
     Kumar].

     Can also be used to modify fill_post_wcc() in NFSD which retrieves
     i_version directly, but has just called vfs_getattr().  It could get
     it from the kstat struct if it used vfs_xgetattr() instead.

     (There's disagreement on the exact semantics of a single field, since
     not all filesystems do this the same way).

 (8) BSD stat compatibility: Including more fields from the BSD stat such
     as creation time (st_btime) and inode generation number (st_gen)
     [Jeremy Allison, Bernd Schubert].

 (9) Inode generation number: Useful for FUSE and userspace NFS servers
     [Bernd Schubert].

     (This was asked for but later deemed unnecessary with the
     open-by-handle capability available and caused disagreement as to
     whether it's a security hole or not).

(10) Extra coherency data may be useful in making backups [Andreas Dilger].

     (No particular data were offered, but things like last backup
     timestamp, the data version number and the DOS archive bit would come
     into this category).

(11) Allow the filesystem to indicate what it can/cannot provide: A
     filesystem can now say it doesn't support a standard stat feature if
     that isn't available, so if, for instance, inode numbers or UIDs don't
     exist or are fabricated locally...

     (This requires a separate system call - I have an fsinfo() call idea
     for this).

(12) Store a 16-byte volume ID in the superblock that can be returned in
     struct xstat [Steve French].

     (Deferred to fsinfo).

(13) Include granularity fields in the time data to indicate the
     granularity of each of the times (NFSv4 time_delta) [Steve French].

     (Deferred to fsinfo).

(14) FS_IOC_GETFLAGS value.  These could be translated to BSD's st_flags.
     Note that the Linux IOC flags are a mess and filesystems such as Ext4
     define flags that aren't in linux/fs.h, so translation in the kernel
     may be a necessity (or, possibly, we provide the filesystem type too).

     (Some attributes are made available in stx_attributes, but the general
     feeling was that the IOC flags were to ext[234]-specific and shouldn't
     be exposed through statx this way).

(15) Mask of features available on file (eg: ACLs, seclabel) [Brad Boyer,
     Michael Kerrisk].

     (Deferred, probably to fsinfo.  Finding out if there's an ACL or
     seclabal might require extra filesystem operations).

(16) Femtosecond-resolution timestamps [Dave Chinner].

     (A __reserved field has been left in the statx_timestamp struct for
     this - if there proves to be a need).

(17) A set multiple attributes syscall to go with this.

===============
NEW SYSTEM CALL
===============

The new system call is:

	int ret = statx(int dfd,
			const char *filename,
			unsigned int flags,
			unsigned int mask,
			struct statx *buffer);

The dfd, filename and flags parameters indicate the file to query, in a
similar way to fstatat().  There is no equivalent of lstat() as that can be
emulated with statx() by passing AT_SYMLINK_NOFOLLOW in flags.  There is
also no equivalent of fstat() as that can be emulated by passing a NULL
filename to statx() with the fd of interest in dfd.

Whether or not statx() synchronises the attributes with the backing store
can be controlled by OR'ing a value into the flags argument (this typically
only affects network filesystems):

 (1) AT_STATX_SYNC_AS_STAT tells statx() to behave as stat() does in this
     respect.

 (2) AT_STATX_FORCE_SYNC will require a network filesystem to synchronise
     its attributes with the server - which might require data writeback to
     occur to get the timestamps correct.

 (3) AT_STATX_DONT_SYNC will suppress synchronisation with the server in a
     network filesystem.  The resulting values should be considered
     approximate.

mask is a bitmask indicating the fields in struct statx that are of
interest to the caller.  The user should set this to STATX_BASIC_STATS to
get the basic set returned by stat().  It should be noted that asking for
more information may entail extra I/O operations.

buffer points to the destination for the data.  This must be 256 bytes in
size.

======================
MAIN ATTRIBUTES RECORD
======================

The following structures are defined in which to return the main attribute
set:

	struct statx_timestamp {
		__s64	tv_sec;
		__s32	tv_nsec;
		__s32	__reserved;
	};

	struct statx {
		__u32	stx_mask;
		__u32	stx_blksize;
		__u64	stx_attributes;
		__u32	stx_nlink;
		__u32	stx_uid;
		__u32	stx_gid;
		__u16	stx_mode;
		__u16	__spare0[1];
		__u64	stx_ino;
		__u64	stx_size;
		__u64	stx_blocks;
		__u64	__spare1[1];
		struct statx_timestamp	stx_atime;
		struct statx_timestamp	stx_btime;
		struct statx_timestamp	stx_ctime;
		struct statx_timestamp	stx_mtime;
		__u32	stx_rdev_major;
		__u32	stx_rdev_minor;
		__u32	stx_dev_major;
		__u32	stx_dev_minor;
		__u64	__spare2[14];
	};

The defined bits in request_mask and stx_mask are:

	STATX_TYPE		Want/got stx_mode & S_IFMT
	STATX_MODE		Want/got stx_mode & ~S_IFMT
	STATX_NLINK		Want/got stx_nlink
	STATX_UID		Want/got stx_uid
	STATX_GID		Want/got stx_gid
	STATX_ATIME		Want/got stx_atime{,_ns}
	STATX_MTIME		Want/got stx_mtime{,_ns}
	STATX_CTIME		Want/got stx_ctime{,_ns}
	STATX_INO		Want/got stx_ino
	STATX_SIZE		Want/got stx_size
	STATX_BLOCKS		Want/got stx_blocks
	STATX_BASIC_STATS	[The stuff in the normal stat struct]
	STATX_BTIME		Want/got stx_btime{,_ns}
	STATX_ALL		[All currently available stuff]

stx_btime is the file creation time, stx_mask is a bitmask indicating the
data provided and __spares*[] are where as-yet undefined fields can be
placed.

Time fields are structures with separate seconds and nanoseconds fields
plus a reserved field in case we want to add even finer resolution.  Note
that times will be negative if before 1970; in such a case, the nanosecond
fields will also be negative if not zero.

The bits defined in the stx_attributes field convey information about a
file, how it is accessed, where it is and what it does.  The following
attributes map to FS_*_FL flags and are the same numerical value:

	STATX_ATTR_COMPRESSED		File is compressed by the fs
	STATX_ATTR_IMMUTABLE		File is marked immutable
	STATX_ATTR_APPEND		File is append-only
	STATX_ATTR_NODUMP		File is not to be dumped
	STATX_ATTR_ENCRYPTED		File requires key to decrypt in fs

Within the kernel, the supported flags are listed by:

	KSTAT_ATTR_FS_IOC_FLAGS

[Are any other IOC flags of sufficient general interest to be exposed
through this interface?]

New flags include:

	STATX_ATTR_AUTOMOUNT		Object is an automount trigger

These are for the use of GUI tools that might want to mark files specially,
depending on what they are.

Fields in struct statx come in a number of classes:

 (0) stx_dev_*, stx_blksize.

     These are local system information and are always available.

 (1) stx_mode, stx_nlinks, stx_uid, stx_gid, stx_[amc]time, stx_ino,
     stx_size, stx_blocks.

     These will be returned whether the caller asks for them or not.  The
     corresponding bits in stx_mask will be set to indicate whether they
     actually have valid values.

     If the caller didn't ask for them, then they may be approximated.  For
     example, NFS won't waste any time updating them from the server,
     unless as a byproduct of updating something requested.

     If the values don't actually exist for the underlying object (such as
     UID or GID on a DOS file), then the bit won't be set in the stx_mask,
     even if the caller asked for the value.  In such a case, the returned
     value will be a fabrication.

     Note that there are instances where the type might not be valid, for
     instance Windows reparse points.

 (2) stx_rdev_*.

     This will be set only if stx_mode indicates we're looking at a
     blockdev or a chardev, otherwise will be 0.

 (3) stx_btime.

     Similar to (1), except this will be set to 0 if it doesn't exist.

=======
TESTING
=======

The following test program can be used to test the statx system call:

	samples/statx/test-statx.c

Just compile and run, passing it paths to the files you want to examine.
The file is built automatically if CONFIG_SAMPLES is enabled.

Here's some example output.  Firstly, an NFS directory that crosses to
another FSID.  Note that the AUTOMOUNT attribute is set because transiting
this directory will cause d_automount to be invoked by the VFS.

	[root@andromeda ~]# /tmp/test-statx -A /warthog/data
	statx(/warthog/data) = 0
	results=7ff
	  Size: 4096            Blocks: 8          IO Block: 1048576  directory
	Device: 00:26           Inode: 1703937     Links: 125
	Access: (3777/drwxrwxrwx)  Uid:     0   Gid:  4041
	Access: 2016-11-24 09:02:12.219699527+0000
	Modify: 2016-11-17 10:44:36.225653653+0000
	Change: 2016-11-17 10:44:36.225653653+0000
	Attributes: 0000000000001000 (-------- -------- -------- -------- -------- -------- ---m---- --------)

Secondly, the result of automounting on that directory.

	[root@andromeda ~]# /tmp/test-statx /warthog/data
	statx(/warthog/data) = 0
	results=7ff
	  Size: 4096            Blocks: 8          IO Block: 1048576  directory
	Device: 00:27           Inode: 2           Links: 125
	Access: (3777/drwxrwxrwx)  Uid:     0   Gid:  4041
	Access: 2016-11-24 09:02:12.219699527+0000
	Modify: 2016-11-17 10:44:36.225653653+0000
	Change: 2016-11-17 10:44:36.225653653+0000

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2017-03-02 20:51:15 -05:00
Ingo Molnar
174cd4b1e5 sched/headers: Prepare to move signal wakeup & sigpending methods from <linux/sched.h> into <linux/sched/signal.h>
Fix up affected files that include this signal functionality via sched.h.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-03-02 08:42:32 +01:00
Ingo Molnar
5b825c3af1 sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h>
Add #include <linux/cred.h> dependencies to all .c files rely on sched.h
doing that for them.

Note that even if the count where we need to add extra headers seems high,
it's still a net win, because <linux/sched.h> is included in over
2,200 files ...

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-03-02 08:42:31 +01:00
Konstantin Khlebnikov
51f8f3c4e2 ovl: drop CAP_SYS_RESOURCE from saved mounter's credentials
If overlay was mounted by root then quota set for upper layer does not work
because overlay now always use mounter's credentials for operations.
Also overlay might deplete reserved space and inodes in ext4.

This patch drops capability SYS_RESOURCE from saved credentials.
This affects creation new files, whiteouts, and copy-up operations.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Fixes: 1175b6b8d9 ("ovl: do operations on underlying file system in mounter's context")
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-02-07 15:47:14 +01:00
Amir Goldstein
e593b2bf51 ovl: properly implement sync_filesystem()
overlayfs syncs all inode pages on sync_filesystem(), but it also
needs to call s_op->sync_fs() of upper fs for metadata sync.

This fixes correctness of syncfs(2) as demonstrated by following
xfs specific test:

xfs_sync_stats()
{
	echo $1
	echo -n "xfs_log_force = "
	grep log /proc/fs/xfs/stat  | awk '{ print $5 }'
}

xfs_sync_stats "before touch"
touch x
xfs_sync_stats "after touch"
xfs_io -c syncfs .
xfs_sync_stats "after syncfs"
xfs_io -c fsync x
xfs_sync_stats "after fsync"
xfs_io -c fsync x
xfs_sync_stats "after fsync #2"

When this test is run in overlay mount over xfs, log force
count does not increase with syncfs command.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-02-07 15:47:14 +01:00
Amir Goldstein
01ad3eb8a0 ovl: concurrent copy up of regular files
Now that copy up of regular file is done using O_TMPFILE,
we don't need to hold rename_lock throughout copy up.

Use the copy up waitqueue to synchronize concurrent copy up
of the same file. Different regular files can be copied up
concurrently.

The upper dir inode_lock is taken instead of rename_lock,
because it is needed for lookup and later for linking the
temp file, but it is released while copying up data.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-02-07 15:47:14 +01:00
Amir Goldstein
39d3d60a54 ovl: introduce copy up waitqueue
The overlay sb 'copyup_wq' and overlay inode 'copying' condition
variable are about to replace the upper sb rename_lock, as finer
grained synchronization objects for concurrent copy up.

Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-02-07 15:47:14 +01:00
Amir Goldstein
d8514d8edb ovl: copy up regular file using O_TMPFILE
In preparation for concurrent copy up, implement copy up
of regular file as O_TMPFILE that is linked to upperdir
instead of a file in workdir that is moved to upperdir.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-02-07 15:47:14 +01:00
Amir Goldstein
42f269b925 ovl: rearrange code in ovl_copy_up_locked()
As preparation to implementing copy up with O_TMPFILE,
name the variable for dentry before final rename 'temp' and
assign it to 'newdentry' only after rename.

Also lookup upper dentry before looking up temp dentry and
move ovl_set_timestamps() into ovl_copy_up_locked(), because
that is going to be more convenient for upcoming change.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-02-07 15:47:14 +01:00
Amir Goldstein
e7f52429b4 ovl: check if upperdir fs supports O_TMPFILE
This is needed for choosing between concurrent copyup
using O_TMPFILE and legacy copyup using workdir+rename.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-02-07 15:47:14 +01:00
Amir Goldstein
4c7d0c9cb7 ovl: fix possible use after free on redirect dir lookup
ovl_lookup_layer() iterates on path elements of d->name.name
but also frees and allocates a new pointer for d->name.name.

For the case of lookup in upper layer, the initial d->name.name
pointer is stable (dentry->d_name), but for lower layers, the
initial d->name.name can be d->redirect, which can be freed during
iteration.

[SzM]
Keep the count of remaining characters in the redirect path and calculate
the current position from that.  This works becuase only the prefix is
modified, the ending always stays the same.

Fixes: 02b69b284c ("ovl: lookup redirects")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2017-01-18 15:19:54 +01:00
Linus Torvalds
231753ef78 Merge uncontroversial parts of branch 'readlink' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull partial readlink cleanups from Miklos Szeredi.

This is the uncontroversial part of the readlink cleanup patch-set that
simplifies the default readlink handling.

Miklos and Al are still discussing the rest of the series.

* git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  vfs: make generic_readlink() static
  vfs: remove ".readlink = generic_readlink" assignments
  vfs: default to generic_readlink()
  vfs: replace calling i_op->readlink with vfs_readlink()
  proc/self: use generic_readlink
  ecryptfs: use vfs_get_link()
  bad_inode: add missing i_op initializers
2016-12-17 19:16:12 -08:00
Linus Torvalds
ff0f962ca3 Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs updates from Miklos Szeredi:
 "This update contains:

   - try to clone on copy-up

   - allow renaming a directory

   - split source into managable chunks

   - misc cleanups and fixes

  It does not contain the read-only fd data inconsistency fix, which Al
  didn't like. I'll leave that to the next year..."

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (36 commits)
  ovl: fix reStructuredText syntax errors in documentation
  ovl: fix return value of ovl_fill_super
  ovl: clean up kstat usage
  ovl: fold ovl_copy_up_truncate() into ovl_copy_up()
  ovl: create directories inside merged parent opaque
  ovl: opaque cleanup
  ovl: show redirect_dir mount option
  ovl: allow setting max size of redirect
  ovl: allow redirect_dir to default to "on"
  ovl: check for emptiness of redirect dir
  ovl: redirect on rename-dir
  ovl: lookup redirects
  ovl: consolidate lookup for underlying layers
  ovl: fix nested overlayfs mount
  ovl: check namelen
  ovl: split super.c
  ovl: use d_is_dir()
  ovl: simplify lookup
  ovl: check lower existence of rename target
  ovl: rename: simplify handling of lower/merged directory
  ...
2016-12-16 10:58:12 -08:00
Linus Torvalds
9a19a6db37 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs updates from Al Viro:

 - more ->d_init() stuff (work.dcache)

 - pathname resolution cleanups (work.namei)

 - a few missing iov_iter primitives - copy_from_iter_full() and
   friends. Either copy the full requested amount, advance the iterator
   and return true, or fail, return false and do _not_ advance the
   iterator. Quite a few open-coded callers converted (and became more
   readable and harder to fuck up that way) (work.iov_iter)

 - several assorted patches, the big one being logfs removal

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  logfs: remove from tree
  vfs: fix put_compat_statfs64() does not handle errors
  namei: fold should_follow_link() with the step into not-followed link
  namei: pass both WALK_GET and WALK_MORE to should_follow_link()
  namei: invert WALK_PUT logics
  namei: shift interpretation of LOOKUP_FOLLOW inside should_follow_link()
  namei: saner calling conventions for mountpoint_last()
  namei.c: get rid of user_path_parent()
  switch getfrag callbacks to ..._full() primitives
  make skb_add_data,{_nocache}() and skb_copy_to_page_nocache() advance only on success
  [iov_iter] new primitives - copy_from_iter_full() and friends
  don't open-code file_inode()
  ceph: switch to use of ->d_init()
  ceph: unify dentry_operations instances
  lustre: switch to use of ->d_init()
2016-12-16 10:24:44 -08:00
Geliang Tang
313684c48c ovl: fix return value of ovl_fill_super
If kcalloc() failed, the return value of ovl_fill_super() is -EINVAL,
not -ENOMEM. So this patch sets this value to -ENOMEM before calling
kcalloc(), and sets it back to -EINVAL after calling kcalloc().

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Al Viro
32a3d848eb ovl: clean up kstat usage
FWIW, there's a bit of abuse of struct kstat in overlayfs object
creation paths - for one thing, it ends up with a very small subset
of struct kstat (mode + rdev), for another it also needs link in
case of symlinks and ends up passing it separately.

IMO it would be better to introduce a separate object for that.

In principle, we might even lift that thing into general API and switch
 ->mkdir()/->mknod()/->symlink() to identical calling conventions.  Hell
knows, perhaps ->create() as well...

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Amir Goldstein
9aba652190 ovl: fold ovl_copy_up_truncate() into ovl_copy_up()
This removes code duplication.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Amir Goldstein
97c684cc91 ovl: create directories inside merged parent opaque
The benefit of making directories opaque on creation is that lookups can
stop short when they reach the original created directory, instead of
continue lookup the entire depth of parent directory stack.

The best case is overlay with N layers, performing lookup for first level
directory, which exists only in upper.  In that case, there will be only
one lookup instead of N.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Miklos Szeredi
5cf5b477f0 ovl: opaque cleanup
oe->opaque is set for

 a) whiteouts
 b) directories having the "trusted.overlay.opaque" xattr

Case b can be simplified, since setting the xattr always implies setting
oe->opaque.  Also once set, the opaque flag is never cleared.

Don't need to set opaque flag for non-directories.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Amir Goldstein
c5bef3a72b ovl: show redirect_dir mount option
Show the value of redirect_dir in /proc/mounts.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Miklos Szeredi
3ea22a71b6 ovl: allow setting max size of redirect
Add a module option to allow tuning the max size of absolute redirects.
Default is 256.

Size of relative redirects is naturally limited by the the underlying
filesystem's max filename length (usually 255).

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Miklos Szeredi
688ea0e5a0 ovl: allow redirect_dir to default to "on"
This patch introduces a kernel config option and a module param.  Both can
be used independently to turn the default value of redirect_dir on or off.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Amir Goldstein
d15951198e ovl: check for emptiness of redirect dir
Before introducing redirect_dir feature, the condition
!ovl_lower_positive(dentry) for a directory, implied that it is a pure
upper directory, which may be removed if empty.

Now that directory can be redirect, it is possible that upper does not
cover any lower (i.e. !ovl_lower_positive(dentry)), but the directory is a
merge (with redirected path) and maybe non empty.

Check for this case in ovl_remove_upper().

This change fixes the following test case from rename-pop-dir.py
of unionmount-testsuite:

    """Remove dir and rename old name"""
    d = ctx.non_empty_dir()
    d2 = ctx.no_dir()

    ctx.rmdir(d, err=ENOTEMPTY)
    ctx.rename(d, d2)
    ctx.rmdir(d, err=ENOENT)
    ctx.rmdir(d2, err=ENOTEMPTY)

./run --ov rename-pop-dir
/mnt/a/no_dir103: Expected error (Directory not empty) was not produced

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:57 +01:00
Miklos Szeredi
a6c6065511 ovl: redirect on rename-dir
Current code returns EXDEV when a directory would need to be copied up to
move.  We could copy up the directory tree in this case, but there's
another, simpler solution: point to old lower directory from moved upper
directory.

This is achieved with a "trusted.overlay.redirect" xattr storing the path
relative to the root of the overlay.  After such attribute has been set,
the directory can be moved without further actions required.

This is a backward incompatible feature, old kernels won't be able to
correctly mount an overlay containing redirected directories.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Miklos Szeredi
02b69b284c ovl: lookup redirects
If a directory has the "trusted.overlay.redirect" xattr, it means that the
value of the xattr should be used to find the underlying directory on the
next lower layer.

The redirect may be relative or absolute.  Absolute redirects begin with a
slash.

A relative redirect means: instead of the current dentry's name use the
value of the redirect to find the directory in the next lower
layer. Relative redirects must not contain a slash.

An absolute redirect means: look up the directory relative to the root of
the overlay using the value of the redirect in the next lower layer.

Redirects work on lower layers as well.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Miklos Szeredi
e28edc46b8 ovl: consolidate lookup for underlying layers
Use a common helper for lookup of upper and lower layers.  This paves the
way for looking up directory redirects.

No functional change.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Amir Goldstein
48fab5d7c7 ovl: fix nested overlayfs mount
When the upper overlayfs checks "trusted.overlay.*" xattr on the underlying
overlayfs mount, it gets -EPERM, which confuses the upper overlayfs.

Fix this by returning -EOPNOTSUPP instead of -EPERM from
ovl_own_xattr_get() and ovl_own_xattr_set().  This behavior is consistent
with the behavior of ovl_listxattr(), which filters out the private
overlayfs xattrs.

Note: nested overlays are deprecated.  But this change makes sense
regardless: these xattrs are private to the overlay and should always be
hidden.  Hence getting and setting them should indicate this.

[SzMi: Use EOPNOTSUPP instead of ENODATA and use it for both getting and
setting "trusted.overlay." xattrs.  This is a perfectly valid error code
for "we don't support this prefix", which is the case here.]

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Miklos Szeredi
6b2d5fe46f ovl: check namelen
We already calculate f_namelen in statfs as the maximum of the name lengths
provided by the filesystems taking part in the overlay.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Miklos Szeredi
bbb1e54dd5 ovl: split super.c
fs/overlayfs/super.c is the biggest of the overlayfs source files and it
contains various utility functions as well as the rather complicated lookup
code.  Split these parts out to separate files.

Before:

 1446 fs/overlayfs/super.c

After:

  919 fs/overlayfs/super.c
  267 fs/overlayfs/namei.c
  235 fs/overlayfs/util.c
   51 fs/overlayfs/ovl_entry.h

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Miklos Szeredi
2b8c30e9ef ovl: use d_is_dir()
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Miklos Szeredi
8ee6059c58 ovl: simplify lookup
If encountering a non-directory, then stop looking at lower layers.

In this case the oe->opaque flag is not set anymore, which doesn't matter
since existence of lower file is now checked at remove/rename time.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:56 +01:00
Miklos Szeredi
3ee23ff102 ovl: check lower existence of rename target
Check if something exists on the lower layer(s) under the target or rename
to decide if directory needs to be marked "opaque".

Marking opaque is done before the rename, and on failure the marking was
undone.  Also the opaque xattr was removed if the target didn't cover
anything.

This patch changes behavior so that removal of "opaque" is not done in
either of the above cases.  This means that directory may have the opaque
flag even if it doesn't cover anything.  However this shouldn't affect the
performance or semantics of the overalay, while simplifying the code.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
370e55ace5 ovl: rename: simplify handling of lower/merged directory
d_is_dir() is safe to call on a negative dentry.  Use this fact to simplify
handling of the lower or merged directories.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
38e813db61 ovl: get rid of PURE type
The remainging uses of __OVL_PATH_PURE can be replaced by
ovl_dentry_is_opaque().

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
2aff4534b6 ovl: check lower existence when removing
Currently ovl_lookup() checks existence of lower file even if there's a
non-directory on upper (which is always opaque).  This is done so that
remove can decide whether a whiteout is needed or not.

It would be better to defer this check to unlink, since most of the time
the gathered information about opaqueness will be unused.

This adds a helper ovl_lower_positive() that checks if there's anything on
the lower layer(s).

The following patches also introduce changes to how the "opaque" attribute
is updated on directories: this attribute is added when the directory is
creted or moved over a whiteout or object covering something on the lower
layer.  However following changes will allow the attribute to remain on the
directory after being moved, even if the new location doesn't cover
anything.  Because of this, we need to check lower layers even for opaque
directories, so that whiteout is only created when necessary.

This function will later be also used to decide about marking a directory
opaque, so deal with negative dentries as well.  When dealing with
negative, it's enough to check for being a whiteout

If the dentry is positive but not upper then it also obviously needs
whiteout/opaque.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
c412ce4983 ovl: add ovl_dentry_is_whiteout()
And use it instead of ovl_dentry_is_opaque() where appropriate.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
99f5d08e36 ovl: don't check sticky
Since commit 07a2daab49 ("ovl: Copy up underlying inode's ->i_mode to
overlay inode") sticky checking on overlay inode is performed by the vfs,
so checking against sticky on underlying inode is not needed.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
804032fabb ovl: don't check rename to self
This is redundant, the vfs already performed this check (and was broken,
see commit 9409e22acd ("vfs: rename: check backing inode being equal")).

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
ca4c8a3a80 ovl: treat special files like a regular fs
No sense in opening special files on the underlying layers, they work just
as well if opened on the overlay.

Side effect is that it's no longer possible to connect one side of a pipe
opened on overlayfs with the other side opened on the underlying layer.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Miklos Szeredi
6c02cb59e6 ovl: rename ovl_rename2() to ovl_rename()
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:55 +01:00
Amir Goldstein
2ea9846649 ovl: use vfs_clone_file_range() for copy up if possible
When copying up within the same fs, try to use vfs_clone_file_range().
This is very efficient when lower and upper are on the same fs
with file reflink support. If vfs_clone_file_range() fails for any
reason, copy up falls back to the regular data copy code.

Tested correct behavior when lower and upper are on:
1. same ext4 (copy)
2. same xfs + reflink patches + mkfs.xfs (copy)
3. same xfs + reflink patches + mkfs.xfs -m reflink=1 (reflink)
4. different xfs + reflink patches + mkfs.xfs -m reflink=1 (copy)

For comparison, on my laptop, xfstest overlay/001 (copy up of large
sparse files) takes less than 1 second in the xfs reflink setup vs.
25 seconds on the rest of the setups.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:54 +01:00
Miklos Szeredi
31c3a70695 Revert "ovl: get_write_access() in truncate"
This reverts commit 03bea60409.

Commit 4d0c5ba2ff ("vfs: do get_write_access() on upper layer of
overlayfs") makes the writecount checks inside overlayfs superfluous, the
file is already copied up and write access acquired on the upper inode when
ovl_setattr is called with ATTR_SIZE.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-16 11:02:54 +01:00
Miklos Szeredi
dfeef68862 vfs: remove ".readlink = generic_readlink" assignments
If .readlink == NULL implies generic_readlink().

Generated by:

to_del="\.readlink.*=.*generic_readlink"
for i in `git grep -l $to_del`; do sed -i "/$to_del"/d $i; done

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-12-09 16:45:04 +01:00
Al Viro
450630975d don't open-code file_inode()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-12-04 18:29:28 -05:00
Miklos Szeredi
c4fcfc1619 ovl: fix d_real() for stacked fs
Handling of recursion in d_real() is completely broken.  Recursion is only
done in the 'inode != NULL' case.  But when opening the file we have
'inode == NULL' hence d_real() will return an overlay dentry.  This won't
work since overlayfs doesn't define its own file operations, so all file
ops will fail.

Fix by doing the recursion first and the check against the inode second.

Bash script to reproduce the issue written by Quentin:

 - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - -
tmpdir=$(mktemp -d)
pushd ${tmpdir}

mkdir -p {upper,lower,work}
echo -n 'rocks' > lower/ksplice
mount -t overlay level_zero upper -o lowerdir=lower,upperdir=upper,workdir=work
cat upper/ksplice

tmpdir2=$(mktemp -d)
pushd ${tmpdir2}

mkdir -p {upper,work}
mount -t overlay level_one upper -o lowerdir=${tmpdir}/upper,upperdir=upper,workdir=work
ls -l upper/ksplice
cat upper/ksplice
 - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - 

Reported-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 2d902671ce ("vfs: merge .d_select_inode() into .d_real()")
Cc: <stable@vger.kernel.org> # v4.8+
2016-11-29 10:20:24 +01:00
Miklos Szeredi
641089c154 ovl: fsync after copy-up
Make sure the copied up file hits the disk before renaming to the final
destination.  If this is not done then the copy-up may corrupt the data in
the file in case of a crash.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
2016-10-31 14:42:14 +01:00
Miklos Szeredi
b93d4a0eb3 ovl: fix get_acl() on tmpfs
tmpfs doesn't have ->get_acl() because it only uses cached acls.

This fixes the acl tests in pjdfstest when tmpfs is used as the upper layer
of the overlay.

Reported-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 39a25b2b37 ("ovl: define ->get_acl() for overlay inodes")
Cc: <stable@vger.kernel.org> # v4.8
2016-10-31 14:42:14 +01:00
Miklos Szeredi
fd3220d37b ovl: update S_ISGID when setting posix ACLs
This change fixes xfstest generic/375, which failed to clear the
setgid bit in the following test case on overlayfs:

  touch $testfile
  chown 100:100 $testfile
  chmod 2755 $testfile
  _runas -u 100 -g 101 -- setfacl -m u::rwx,g::rwx,o::rwx $testfile

Reported-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Tested-by: Amir Goldstein <amir73il@gmail.com>
Fixes: d837a49bd5 ("ovl: fix POSIX ACL setting")
Cc: <stable@vger.kernel.org> # v4.8
2016-10-31 14:42:14 +01:00
Linus Torvalds
b26b5ef5ec Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull more misc uaccess and vfs updates from Al Viro:
 "The rest of the stuff from -next (more uaccess work) + assorted fixes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  score: traps: Add missing include file to fix build error
  fs/super.c: don't fool lockdep in freeze_super() and thaw_super() paths
  fs/super.c: fix race between freeze_super() and thaw_super()
  overlayfs: Fix setting IOP_XATTR flag
  iov_iter: kernel-doc import_iovec() and rw_copy_check_uvector()
  blackfin: no access_ok() for __copy_{to,from}_user()
  arm64: don't zero in __copy_from_user{,_inatomic}
  arm: don't zero in __copy_from_user_inatomic()/__copy_from_user()
  arc: don't leak bits of kernel stack into coredump
  alpha: get rid of tail-zeroing in __copy_user()
2016-10-14 18:19:05 -07:00
Linus Torvalds
1a892b485f Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs updates from Miklos Szeredi:
 "This update contains fixes to the "use mounter's permission to access
  underlying layers" area, and miscellaneous other fixes and cleanups.

  No new features this time"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: use vfs_get_link()
  vfs: add vfs_get_link() helper
  ovl: use generic_readlink
  ovl: explain error values when removing acl from workdir
  ovl: Fix info leak in ovl_lookup_temp()
  ovl: during copy up, switch to mounter's creds early
  ovl: lookup: do getxattr with mounter's permission
  ovl: copy_up_xattr(): use strnlen
2016-10-14 17:23:33 -07:00
Vivek Goyal
655042cc14 overlayfs: Fix setting IOP_XATTR flag
ovl_fill_super calls ovl_new_inode to create a root inode for the new
superblock before initializing sb->s_xattr.  This wrongly causes
IOP_XATTR to be cleared in i_opflags of the new inode, causing SELinux
to log the following message:

  SELinux: (dev overlay, type overlay) has no xattr support

Fix this by initializing sb->s_xattr and similar fields before calling
ovl_new_inode.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-14 20:00:34 -04:00
Miklos Szeredi
7764235bec ovl: use vfs_get_link()
Resulting in a complete removal of a function basically implementing the
inverse of vfs_readlink().

As a bonus, now the proper security hook is also called.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-10-14 11:16:47 +02:00
Miklos Szeredi
78a3fa4f32 ovl: use generic_readlink
All filesystems that are backers for overlayfs would also use
generic_readlink().  Move this logic to the overlay itself, which is a nice
cleanup.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-10-14 11:16:46 +02:00
Miklos Szeredi
cb348edb6b ovl: explain error values when removing acl from workdir
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> 
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-10-14 11:16:46 +02:00
Linus Torvalds
101105b171 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull more vfs updates from Al Viro:
 ">rename2() work from Miklos + current_time() from Deepa"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: Replace current_fs_time() with current_time()
  fs: Replace CURRENT_TIME_SEC with current_time() for inode timestamps
  fs: Replace CURRENT_TIME with current_time() for inode timestamps
  fs: proc: Delete inode time initializations in proc_alloc_inode()
  vfs: Add current_time() api
  vfs: add note about i_op->rename changes to porting
  fs: rename "rename2" i_op to "rename"
  vfs: remove unused i_op->rename
  fs: make remaining filesystems use .rename2
  libfs: support RENAME_NOREPLACE in simple_rename()
  fs: support RENAME_NOREPLACE for local filesystems
  ncpfs: fix unused variable warning
2016-10-10 20:16:43 -07:00
Linus Torvalds
97d2116708 Merge branch 'work.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs xattr updates from Al Viro:
 "xattr stuff from Andreas

  This completes the switch to xattr_handler ->get()/->set() from
  ->getxattr/->setxattr/->removexattr"

* 'work.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: Remove {get,set,remove}xattr inode operations
  xattr: Stop calling {get,set,remove}xattr inode operations
  vfs: Check for the IOP_XATTR flag in listxattr
  xattr: Add __vfs_{get,set,remove}xattr helpers
  libfs: Use IOP_XATTR flag for empty directory handling
  vfs: Use IOP_XATTR flag for bad-inode handling
  vfs: Add IOP_XATTR inode operations flag
  vfs: Move xattr_resolve_name to the front of fs/xattr.c
  ecryptfs: Switch to generic xattr handlers
  sockfs: Get rid of getxattr iop
  sockfs: getxattr: Fail with -EOPNOTSUPP for invalid attribute names
  kernfs: Switch to generic xattr handlers
  hfs: Switch to generic xattr handlers
  jffs2: Remove jffs2_{get,set,remove}xattr macros
  xattr: Remove unnecessary NULL attribute name check
2016-10-10 17:11:50 -07:00
Linus Torvalds
abb5a14fa2 Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull misc vfs updates from Al Viro:
 "Assorted misc bits and pieces.

  There are several single-topic branches left after this (rename2
  series from Miklos, current_time series from Deepa Dinamani, xattr
  series from Andreas, uaccess stuff from from me) and I'd prefer to
  send those separately"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (39 commits)
  proc: switch auxv to use of __mem_open()
  hpfs: support FIEMAP
  cifs: get rid of unused arguments of CIFSSMBWrite()
  posix_acl: uapi header split
  posix_acl: xattr representation cleanups
  fs/aio.c: eliminate redundant loads in put_aio_ring_file
  fs/internal.h: add const to ns_dentry_operations declaration
  compat: remove compat_printk()
  fs/buffer.c: make __getblk_slow() static
  proc: unsigned file descriptors
  fs/file: more unsigned file descriptors
  fs: compat: remove redundant check of nr_segs
  cachefiles: Fix attempt to read i_blocks after deleting file [ver #2]
  cifs: don't use memcpy() to copy struct iov_iter
  get rid of separate multipage fault-in primitives
  fs: Avoid premature clearing of capabilities
  fs: Give dentry to inode_change_ok() instead of inode
  fuse: Propagate dentry down to inode_change_ok()
  ceph: Propagate dentry down to inode_change_ok()
  xfs: Propagate dentry down to inode_change_ok()
  ...
2016-10-10 13:04:49 -07:00
Al Viro
e55f1d1d13 Merge remote-tracking branch 'jk/vfs' into work.misc 2016-10-08 11:06:08 -04:00
Andreas Gruenbacher
fd50ecaddf vfs: Remove {get,set,remove}xattr inode operations
These inode operations are no longer used; remove them.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-07 21:48:36 -04:00
Andreas Gruenbacher
5d6c31910b xattr: Add __vfs_{get,set,remove}xattr helpers
Right now, various places in the kernel check for the existence of
getxattr, setxattr, and removexattr inode operations and directly call
those operations.  Switch to helper functions and test for the IOP_XATTR
flag instead.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-10-07 20:10:44 -04:00
Linus Torvalds
a3443cda55 Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull security subsystem updates from James Morris:

  SELinux/LSM:
   - overlayfs support, necessary for container filesystems

  LSM:
   - finally remove the kernel_module_from_file hook

  Smack:
   - treat signal delivery as an 'append' operation

  TPM:
   - lots of bugfixes & updates

  Audit:
   - new audit data type: LSM_AUDIT_DATA_FILE

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (47 commits)
  Revert "tpm/tpm_crb: implement tpm crb idle state"
  Revert "tmp/tpm_crb: fix Intel PTT hw bug during idle state"
  Revert "tpm/tpm_crb: open code the crb_init into acpi_add"
  Revert "tmp/tpm_crb: implement runtime pm for tpm_crb"
  lsm,audit,selinux: Introduce a new audit data type LSM_AUDIT_DATA_FILE
  tmp/tpm_crb: implement runtime pm for tpm_crb
  tpm/tpm_crb: open code the crb_init into acpi_add
  tmp/tpm_crb: fix Intel PTT hw bug during idle state
  tpm/tpm_crb: implement tpm crb idle state
  tpm: add check for minimum buffer size in tpm_transmit()
  tpm: constify TPM 1.x header structures
  tpm/tpm_crb: fix the over 80 characters checkpatch warring
  tpm/tpm_crb: drop useless cpu_to_le32 when writing to registers
  tpm/tpm_crb: cache cmd_size register value.
  tmp/tpm_crb: drop include to platform_device
  tpm/tpm_tis: remove unused itpm variable
  tpm_crb: fix incorrect values of cmdReady and goIdle bits
  tpm_crb: refine the naming of constants
  tpm_crb: remove wmb()'s
  tpm_crb: fix crb_req_canceled behavior
  ...
2016-10-04 14:48:27 -07:00
Miklos Szeredi
2773bf00ae fs: rename "rename2" i_op to "rename"
Generated patch:

sed -i "s/\.rename2\t/\.rename\t\t/" `git grep -wl rename2`
sed -i "s/\brename2\b/rename/g" `git grep -wl rename2`

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-27 11:03:58 +02:00
Jan Kara
31051c85b5 fs: Give dentry to inode_change_ok() instead of inode
inode_change_ok() will be resposible for clearing capabilities and IMA
extended attributes and as such will need dentry. Give it as an argument
to inode_change_ok() instead of an inode. Also rename inode_change_ok()
to setattr_prepare() to better relect that it does also some
modifications in addition to checks.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
2016-09-22 10:56:19 +02:00
Richard Weinberger
6a45b3628c ovl: Fix info leak in ovl_lookup_temp()
The function uses the memory address of a struct dentry as unique id.
While the address-based directory entry is only visible to root it is IMHO
still worth fixing since the temporary name does not have to be a kernel
address.  It can be any unique number.  Replace it by an atomic integer
which is allowed to wrap around.

Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org> # v3.18+
Fixes: e9be9d5e76 ("overlay filesystem")
2016-09-21 16:37:07 +02:00
Vivek Goyal
8eac98b8be ovl: during copy up, switch to mounter's creds early
Now, we have the notion that copy up of a file is done with the creds
of mounter of overlay filesystem (as opposed to task). Right now before
we switch creds, we do some vfs_getattr() operations in the context of
task and that itself can fail. We should do that getattr() using the
creds of mounter instead.

So this patch switches to mounter's creds early during copy up process so
that even vfs_getattr() is done with mounter's creds.

Do not call revert_creds() unless we have already called
ovl_override_creds(). [Reported by Arnd Bergmann]

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-19 16:50:59 +02:00
Miklos Szeredi
2b6bc7f48d ovl: lookup: do getxattr with mounter's permission
The getxattr() in ovl_is_opaquedir() was missed when converting all
operations on underlying fs to be done under mounter's permission.

This patch fixes this by moving the ovl_override_creds()/revert_creds() out
from ovl_lookup_real() to ovl_lookup().

Also convert to using vfs_getxattr() instead of directly calling
i_op->getxattr().

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-16 14:12:11 +02:00
Miklos Szeredi
8b326c61de ovl: copy_up_xattr(): use strnlen
Be defensive about what underlying fs provides us in the returned xattr
list buffer.  strlen() may overrun the buffer, so use strnlen() and WARN if
the contents are not properly null terminated.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
2016-09-16 14:12:11 +02:00
Miklos Szeredi
c568d68341 locks: fix file locking on overlayfs
This patch allows flock, posix locks, ofd locks and leases to work
correctly on overlayfs.

Instead of using the underlying inode for storing lock context use the
overlay inode.  This allows locks to be persistent across copy-up.

This is done by introducing locks_inode() helper and using it instead of
file_inode() to get the inode in locking code.  For non-overlayfs the two
are equivalent, except for an extra pointer dereference in locks_inode().

Since lock operations are in "struct file_operations" we must also make
sure not to call underlying filesystem's lock operations.  Introcude a
super block flag MS_NOREMOTELOCK to this effect.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: Jeff Layton <jlayton@poochiereds.net>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
2016-09-16 12:44:20 +02:00
Miklos Szeredi
e1ff3dd1ae ovl: fix workdir creation
Workdir creation fails in latest kernel.

Fix by allowing EOPNOTSUPP as a valid return value from
vfs_removexattr(XATTR_NAME_POSIX_ACL_*).  Upper filesystem may not support
ACL and still be perfectly able to support overlayfs.

Reported-by: Martin Ziegler <ziegler@uni-freiburg.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: c11b9fdd6a ("ovl: remove posix_acl_default from workdir")
Cc: <stable@vger.kernel.org>
2016-09-05 13:55:20 +02:00
Miklos Szeredi
7cb35119d0 ovl: listxattr: use strnlen()
Be defensive about what underlying fs provides us in the returned xattr
list buffer.  If it's not properly null terminated, bail out with a warning
insead of BUG.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
2016-09-01 11:12:00 +02:00
Andreas Gruenbacher
0eb45fc3bb ovl: Switch to generic_getxattr
Now that overlayfs has xattr handlers for iop->{set,remove}xattr, use
those same handlers for iop->getxattr as well.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:12:00 +02:00
Miklos Szeredi
ce31513a91 ovl: copyattr after setting POSIX ACL
Setting POSIX acl may also modify the file mode, so need to copy that up to
the overlay inode.

Reported-by: Eryu Guan <eguan@redhat.com>
Fixes: d837a49bd5 ("ovl: fix POSIX ACL setting")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:12:00 +02:00
Andreas Gruenbacher
0e585ccc13 ovl: Switch to generic_removexattr
Commit d837a49bd5 ("ovl: fix POSIX ACL setting") switches from
iop->setxattr from ovl_setxattr to generic_setxattr, so switch from
ovl_removexattr to generic_removexattr as well.  As far as permission
checking goes, the same rules should apply in either case.

While doing that, rename ovl_setxattr to ovl_xattr_set to indicate that
this is not an iop->setxattr implementation and remove the unused inode
argument.

Move ovl_other_xattr_set above ovl_own_xattr_set so that they match the
order of handlers in ovl_xattr_handlers.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Fixes: d837a49bd5 ("ovl: fix POSIX ACL setting")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:12:00 +02:00
Andreas Gruenbacher
0c97be22f9 ovl: Get rid of ovl_xattr_noacl_handlers array
Use an ordinary #ifdef to conditionally include the POSIX ACL handlers
in ovl_xattr_handlers, like the other filesystems do.  Flag the code
that is now only used conditionally with __maybe_unused.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:11:59 +02:00
Andreas Gruenbacher
fe2b759523 ovl: Fix OVL_XATTR_PREFIX
Make sure ovl_own_xattr_handler only matches attribute names starting
with "overlay.", not "overlayXXX".

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Fixes: d837a49bd5 ("ovl: fix POSIX ACL setting")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:11:59 +02:00
Colin Ian King
fd36570a88 ovl: fix spelling mistake: "directries" -> "directories"
Trivial fix to spelling mistake in pr_err message.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:11:59 +02:00
Miklos Szeredi
2a3a2a3f35 ovl: don't cache acl on overlay layer
Some operations (setxattr/chmod) can make the cached acl stale.  We either
need to clear overlay's acl cache for the affected inode or prevent acl
caching on the overlay altogether.  Preventing caching has the following
advantages:

 - no double caching, less memory used

 - overlay cache doesn't go stale when fs clears it's own cache

Possible disadvantage is performance loss.  If that becomes a problem
get_acl() can be optimized for overlayfs.

This patch disables caching by pre setting i_*acl to a value that

  - has bit 0 set, so is_uncached_acl() will return true

  - is not equal to ACL_NOT_CACHED, so get_acl() will not overwrite it

The constant -3 was chosen for this purpose.

Fixes: 39a25b2b37 ("ovl: define ->get_acl() for overlay inodes")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:11:59 +02:00
Miklos Szeredi
5201dc449e ovl: use cached acl on underlying layer
Instead of calling ->get_acl() directly, use get_acl() to get the cached
value.

We will have the acl cached on the underlying inode anyway, because we do
permission checking on the both the overlay and the underlying fs.

So, since we already have double caching, this improves performance without
any cost.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2016-09-01 11:11:59 +02:00
Miklos Szeredi
eea2fb4851 ovl: proper cleanup of workdir
When mounting overlayfs it needs a clean "work" directory under the
supplied workdir.

Previously the mount code removed this directory if it already existed and
created a new one.  If the removal failed (e.g. directory was not empty)
then it fell back to a read-only mount not using the workdir.

While this has never been reported, it is possible to get a non-empty
"work" dir from a previous mount of overlayfs in case of crash in the
middle of an operation using the work directory.

In this case the left over state should be discarded and the overlay
filesystem will be consistent, guaranteed by the atomicity of operations on
moving to/from the workdir to the upper layer.

This patch implements cleaning out any files left in workdir.  It is
implemented using real recursion for simplicity, but the depth is limited
to 2, because the worst case is that of a directory containing whiteouts
under "work".

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org>
2016-09-01 11:11:59 +02:00