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ovl: check IS_APPEND() on real upper inode

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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>
This commit is contained in:
Amir Goldstein 2017-04-08 14:49:07 +03:00 committed by Miklos Szeredi
parent 78757af651
commit b0990fbbbd
1 changed files with 25 additions and 3 deletions
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28
fs/overlayfs/super.c
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@ -49,11 +49,28 @@ static void ovl_dentry_release(struct dentry *dentry)
}
}
static int ovl_check_append_only(struct inode *inode, int flag)
{
/*
* This test was moot in vfs may_open() because overlay inode does
* not have the S_APPEND flag, so re-check on real upper inode
*/
if (IS_APPEND(inode)) {
if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
return -EPERM;
if (flag & O_TRUNC)
return -EPERM;
}
return 0;
}
static struct dentry *ovl_d_real(struct dentry *dentry,
const struct inode *inode,
unsigned int open_flags)
{
struct dentry *real;
int err;
if (!d_is_reg(dentry)) {
if (!inode || inode == d_inode(dentry))
@ -65,15 +82,20 @@ static struct dentry *ovl_d_real(struct dentry *dentry,
return dentry;
if (open_flags) {
int err = ovl_open_maybe_copy_up(dentry, open_flags);
err = ovl_open_maybe_copy_up(dentry, open_flags);
if (err)
return ERR_PTR(err);
}
real = ovl_dentry_upper(dentry);
if (real && (!inode || inode == d_inode(real)))
if (real && (!inode || inode == d_inode(real))) {
if (!inode) {
err = ovl_check_append_only(d_inode(real), open_flags);
if (err)
return ERR_PTR(err);
}
return real;
}
real = ovl_dentry_lower(dentry);
if (!real)