overlayfs fixes for 4.19-rc4

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Merge tag 'ovl-fixes-4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs fixes from Miklos Szeredi:
 "This fixes a regression in the recent file stacking update, reported
  and fixed by Amir Goldstein. The fix is fairly trivial, but involves
  adding a fadvise() f_op and the associated churn in the vfs. As
  discussed on -fsdevel, there are other possible uses for this method,
  than allowing proper stacking for overlays.

  And there's one other fix for a syzkaller detected oops"

* tag 'ovl-fixes-4.19-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fix oopses in ovl_fill_super() failure paths
  ovl: add ovl_fadvise()
  vfs: implement readahead(2) using POSIX_FADV_WILLNEED
  vfs: add the fadvise() file operation
  Documentation/filesystems: update documentation of file_operations
  ovl: fix GPF in swapfile_activate of file from overlayfs over xfs
  ovl: respect FIEMAP_FLAG_SYNC flag

Documentation/filesystems/vfs.txt

@@ -848,7 +848,7 @@ struct file_operations
 ----------------------
 
 This describes how the VFS can manipulate an open file. As of kernel
-4.1, the following members are defined:
+4.18, the following members are defined:
 
 struct file_operations {
 	struct module *owner;
@@ -858,11 +858,11 @@ struct file_operations {
 	ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
 	ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
 	int (*iterate) (struct file *, struct dir_context *);
+	int (*iterate_shared) (struct file *, struct dir_context *);
 	__poll_t (*poll) (struct file *, struct poll_table_struct *);
 	long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
 	long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
 	int (*mmap) (struct file *, struct vm_area_struct *);
-	int (*mremap)(struct file *, struct vm_area_struct *);
 	int (*open) (struct inode *, struct file *);
 	int (*flush) (struct file *, fl_owner_t id);
 	int (*release) (struct inode *, struct file *);
@@ -882,6 +882,10 @@ struct file_operations {
 #ifndef CONFIG_MMU
 	unsigned (*mmap_capabilities)(struct file *);
 #endif
+	ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, loff_t, size_t, unsigned int);
+	int (*clone_file_range)(struct file *, loff_t, struct file *, loff_t, u64);
+	int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t, u64);
+	int (*fadvise)(struct file *, loff_t, loff_t, int);
 };
 
 Again, all methods are called without any locks being held, unless
@@ -899,6 +903,9 @@ otherwise noted.
 
   iterate: called when the VFS needs to read the directory contents
 
+  iterate_shared: called when the VFS needs to read the directory contents
+	when filesystem supports concurrent dir iterators
+
   poll: called by the VFS when a process wants to check if there is
 	activity on this file and (optionally) go to sleep until there
 	is activity. Called by the select(2) and poll(2) system calls
@@ -951,6 +958,16 @@ otherwise noted.
 
   fallocate: called by the VFS to preallocate blocks or punch a hole.
 
+  copy_file_range: called by the copy_file_range(2) system call.
+
+  clone_file_range: called by the ioctl(2) system call for FICLONERANGE and
+	FICLONE commands.
+
+  dedupe_file_range: called by the ioctl(2) system call for FIDEDUPERANGE
+	command.
+
+  fadvise: possibly called by the fadvise64() system call.
+
 Note that the file operations are implemented by the specific
 filesystem in which the inode resides. When opening a device node
 (character or block special) most filesystems will call special

fs/overlayfs/file.c

@@ -131,9 +131,6 @@ static int ovl_open(struct inode *inode, struct file *file)
 	if (IS_ERR(realfile))
 		return PTR_ERR(realfile);
 
-	/* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
-	file->f_mapping = realfile->f_mapping;
-
 	file->private_data = realfile;
 
 	return 0;
@@ -334,6 +331,25 @@ static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len
 	return ret;
 }
 
+static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+	struct fd real;
+	const struct cred *old_cred;
+	int ret;
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		return ret;
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	ret = vfs_fadvise(real.file, offset, len, advice);
+	revert_creds(old_cred);
+
+	fdput(real);
+
+	return ret;
+}
+
 static long ovl_real_ioctl(struct file *file, unsigned int cmd,
 			   unsigned long arg)
 {
@@ -502,6 +518,7 @@ const struct file_operations ovl_file_operations = {
 	.fsync		= ovl_fsync,
 	.mmap		= ovl_mmap,
 	.fallocate	= ovl_fallocate,
+	.fadvise	= ovl_fadvise,
 	.unlocked_ioctl	= ovl_ioctl,
 	.compat_ioctl	= ovl_compat_ioctl,
 

fs/overlayfs/inode.c

@@ -467,6 +467,10 @@ static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		return -EOPNOTSUPP;
 
 	old_cred = ovl_override_creds(inode->i_sb);
+
+	if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC)
+		filemap_write_and_wait(realinode->i_mapping);
+
 	err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
 	revert_creds(old_cred);
 
@@ -500,6 +504,11 @@ static const struct inode_operations ovl_special_inode_operations = {
 	.update_time	= ovl_update_time,
 };
 
+const struct address_space_operations ovl_aops = {
+	/* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
+	.direct_IO		= noop_direct_IO,
+};
+
 /*
  * It is possible to stack overlayfs instance on top of another
  * overlayfs instance as lower layer. We need to annonate the
@@ -571,6 +580,7 @@ static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev,
 	case S_IFREG:
 		inode->i_op = &ovl_file_inode_operations;
 		inode->i_fop = &ovl_file_operations;
+		inode->i_mapping->a_ops = &ovl_aops;
 		break;
 
 	case S_IFDIR:

fs/overlayfs/super.c

@@ -982,16 +982,6 @@ static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
 	if (err)
 		goto out;
 
-	err = -EBUSY;
-	if (ovl_inuse_trylock(upperpath->dentry)) {
-		ofs->upperdir_locked = true;
-	} else if (ofs->config.index) {
-		pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
-		goto out;
-	} else {
-		pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
-	}
-
 	upper_mnt = clone_private_mount(upperpath);
 	err = PTR_ERR(upper_mnt);
 	if (IS_ERR(upper_mnt)) {
@@ -1002,6 +992,17 @@ static int ovl_get_upper(struct ovl_fs *ofs, struct path *upperpath)
 	/* Don't inherit atime flags */
 	upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
 	ofs->upper_mnt = upper_mnt;
+
+	err = -EBUSY;
+	if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) {
+		ofs->upperdir_locked = true;
+	} else if (ofs->config.index) {
+		pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
+		goto out;
+	} else {
+		pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
+	}
+
 	err = 0;
 out:
 	return err;
@@ -1101,8 +1102,10 @@ static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
 		goto out;
 	}
 
+	ofs->workbasedir = dget(workpath.dentry);
+
 	err = -EBUSY;
-	if (ovl_inuse_trylock(workpath.dentry)) {
+	if (ovl_inuse_trylock(ofs->workbasedir)) {
 		ofs->workdir_locked = true;
 	} else if (ofs->config.index) {
 		pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
@@ -1111,7 +1114,6 @@ static int ovl_get_workdir(struct ovl_fs *ofs, struct path *upperpath)
 		pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
 	}
 
-	ofs->workbasedir = dget(workpath.dentry);
 	err = ovl_make_workdir(ofs, &workpath);
 	if (err)
 		goto out;

include/linux/fs.h

@@ -1763,6 +1763,7 @@ struct file_operations {
 			u64);
 	int (*dedupe_file_range)(struct file *, loff_t, struct file *, loff_t,
 			u64);
+	int (*fadvise)(struct file *, loff_t, loff_t, int);
 } __randomize_layout;
 
 struct inode_operations {
@@ -3459,4 +3460,8 @@ static inline bool dir_relax_shared(struct inode *inode)
 extern bool path_noexec(const struct path *path);
 extern void inode_nohighmem(struct inode *inode);
 
+/* mm/fadvise.c */
+extern int vfs_fadvise(struct file *file, loff_t offset, loff_t len,
+		       int advice);
+
 #endif /* _LINUX_FS_H */

mm/Makefile

@@ -32,7 +32,7 @@ ifdef CONFIG_CROSS_MEMORY_ATTACH
 mmu-$(CONFIG_MMU)	+= process_vm_access.o
 endif
 
-obj-y			:= filemap.o mempool.o oom_kill.o \
+obj-y			:= filemap.o mempool.o oom_kill.o fadvise.o \
 			   maccess.o page_alloc.o page-writeback.o \
 			   readahead.o swap.o truncate.o vmscan.o shmem.o \
 			   util.o mmzone.o vmstat.o backing-dev.o \
@@ -49,7 +49,6 @@ else
 	obj-y		+= bootmem.o
 endif
 
-obj-$(CONFIG_ADVISE_SYSCALLS)	+= fadvise.o
 ifdef CONFIG_MMU
 	obj-$(CONFIG_ADVISE_SYSCALLS)	+= madvise.o
 endif

mm/fadvise.c

@@ -27,9 +27,9 @@
  * deactivate the pages and clear PG_Referenced.
  */
 
-int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
+static int generic_fadvise(struct file *file, loff_t offset, loff_t len,
+			   int advice)
 {
-	struct fd f = fdget(fd);
 	struct inode *inode;
 	struct address_space *mapping;
 	struct backing_dev_info *bdi;
@@ -37,22 +37,14 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 	pgoff_t start_index;
 	pgoff_t end_index;
 	unsigned long nrpages;
-	int ret = 0;
 
-	if (!f.file)
-		return -EBADF;
+	inode = file_inode(file);
+	if (S_ISFIFO(inode->i_mode))
+		return -ESPIPE;
 
-	inode = file_inode(f.file);
-	if (S_ISFIFO(inode->i_mode)) {
-		ret = -ESPIPE;
-		goto out;
-	}
-
-	mapping = f.file->f_mapping;
-	if (!mapping || len < 0) {
-		ret = -EINVAL;
-		goto out;
-	}
+	mapping = file->f_mapping;
+	if (!mapping || len < 0)
+		return -EINVAL;
 
 	bdi = inode_to_bdi(mapping->host);
 
@@ -67,9 +59,9 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 			/* no bad return value, but ignore advice */
 			break;
 		default:
-			ret = -EINVAL;
+			return -EINVAL;
 		}
-		goto out;
+		return 0;
 	}
 
 	/*
@@ -85,21 +77,21 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 
 	switch (advice) {
 	case POSIX_FADV_NORMAL:
-		f.file->f_ra.ra_pages = bdi->ra_pages;
-		spin_lock(&f.file->f_lock);
-		f.file->f_mode &= ~FMODE_RANDOM;
-		spin_unlock(&f.file->f_lock);
+		file->f_ra.ra_pages = bdi->ra_pages;
+		spin_lock(&file->f_lock);
+		file->f_mode &= ~FMODE_RANDOM;
+		spin_unlock(&file->f_lock);
 		break;
 	case POSIX_FADV_RANDOM:
-		spin_lock(&f.file->f_lock);
-		f.file->f_mode |= FMODE_RANDOM;
-		spin_unlock(&f.file->f_lock);
+		spin_lock(&file->f_lock);
+		file->f_mode |= FMODE_RANDOM;
+		spin_unlock(&file->f_lock);
 		break;
 	case POSIX_FADV_SEQUENTIAL:
-		f.file->f_ra.ra_pages = bdi->ra_pages * 2;
-		spin_lock(&f.file->f_lock);
-		f.file->f_mode &= ~FMODE_RANDOM;
-		spin_unlock(&f.file->f_lock);
+		file->f_ra.ra_pages = bdi->ra_pages * 2;
+		spin_lock(&file->f_lock);
+		file->f_mode &= ~FMODE_RANDOM;
+		spin_unlock(&file->f_lock);
 		break;
 	case POSIX_FADV_WILLNEED:
 		/* First and last PARTIAL page! */
@@ -115,8 +107,7 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 		 * Ignore return value because fadvise() shall return
 		 * success even if filesystem can't retrieve a hint,
 		 */
-		force_page_cache_readahead(mapping, f.file, start_index,
-					   nrpages);
+		force_page_cache_readahead(mapping, file, start_index, nrpages);
 		break;
 	case POSIX_FADV_NOREUSE:
 		break;
@@ -183,9 +174,32 @@ int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
 		}
 		break;
 	default:
-		ret = -EINVAL;
+		return -EINVAL;
 	}
-out:
+	return 0;
+}
+
+int vfs_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+	if (file->f_op->fadvise)
+		return file->f_op->fadvise(file, offset, len, advice);
+
+	return generic_fadvise(file, offset, len, advice);
+}
+EXPORT_SYMBOL(vfs_fadvise);
+
+#ifdef CONFIG_ADVISE_SYSCALLS
+
+int ksys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
+{
+	struct fd f = fdget(fd);
+	int ret;
+
+	if (!f.file)
+		return -EBADF;
+
+	ret = vfs_fadvise(f.file, offset, len, advice);
+
 	fdput(f);
 	return ret;
 }
@@ -203,3 +217,4 @@ SYSCALL_DEFINE4(fadvise64, int, fd, loff_t, offset, size_t, len, int, advice)
 }
 
 #endif
+#endif

mm/readahead.c

@@ -20,6 +20,7 @@
 #include <linux/file.h>
 #include <linux/mm_inline.h>
 #include <linux/blk-cgroup.h>
+#include <linux/fadvise.h>
 
 #include "internal.h"
 
@@ -575,24 +576,6 @@ page_cache_async_readahead(struct address_space *mapping,
 }
 EXPORT_SYMBOL_GPL(page_cache_async_readahead);
 
-static ssize_t
-do_readahead(struct address_space *mapping, struct file *filp,
-	     pgoff_t index, unsigned long nr)
-{
-	if (!mapping || !mapping->a_ops)
-		return -EINVAL;
-
-	/*
-	 * Readahead doesn't make sense for DAX inodes, but we don't want it
-	 * to report a failure either.  Instead, we just return success and
-	 * don't do any work.
-	 */
-	if (dax_mapping(mapping))
-		return 0;
-
-	return force_page_cache_readahead(mapping, filp, index, nr);
-}
-
 ssize_t ksys_readahead(int fd, loff_t offset, size_t count)
 {
 	ssize_t ret;
@@ -600,16 +583,22 @@ ssize_t ksys_readahead(int fd, loff_t offset, size_t count)
 
 	ret = -EBADF;
 	f = fdget(fd);
-	if (f.file) {
-		if (f.file->f_mode & FMODE_READ) {
-			struct address_space *mapping = f.file->f_mapping;
-			pgoff_t start = offset >> PAGE_SHIFT;
-			pgoff_t end = (offset + count - 1) >> PAGE_SHIFT;
-			unsigned long len = end - start + 1;
-			ret = do_readahead(mapping, f.file, start, len);
-		}
-		fdput(f);
-	}
+	if (!f.file || !(f.file->f_mode & FMODE_READ))
+		goto out;
+
+	/*
+	 * The readahead() syscall is intended to run only on files
+	 * that can execute readahead. If readahead is not possible
+	 * on this file, then we must return -EINVAL.
+	 */
+	ret = -EINVAL;
+	if (!f.file->f_mapping || !f.file->f_mapping->a_ops ||
+	    !S_ISREG(file_inode(f.file)->i_mode))
+		goto out;
+
+	ret = vfs_fadvise(f.file, offset, count, POSIX_FADV_WILLNEED);
+out:
+	fdput(f);
 	return ret;
 }