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

3 files changed, 44 insertions, 15 deletions

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 32e9282893c9..aeaefd2a551b 100644
--- a/fs/overlayfs/file.c
+++ b/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,
 
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index e0bb217c01e2..b6ac545b5a32 100644
--- a/fs/overlayfs/inode.c
+++ b/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:
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 2e0fc93c2c06..30adc9d408a0 100644
--- a/fs/overlayfs/super.c
+++ b/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;