| From d8ac76cdd1755b21e8c008c28d0b7251c0b14986 Mon Sep 17 00:00:00 2001 |
| From: Filipe Manana <fdmanana@suse.com> |
| Date: Wed, 9 Jun 2021 11:25:03 +0100 |
| Subject: btrfs: send: fix invalid path for unlink operations after parent orphanization |
| |
| From: Filipe Manana <fdmanana@suse.com> |
| |
| commit d8ac76cdd1755b21e8c008c28d0b7251c0b14986 upstream. |
| |
| During an incremental send operation, when processing the new references |
| for the current inode, we might send an unlink operation for another inode |
| that has a conflicting path and has more than one hard link. However this |
| path was computed and cached before we processed previous new references |
| for the current inode. We may have orphanized a directory of that path |
| while processing a previous new reference, in which case the path will |
| be invalid and cause the receiver process to fail. |
| |
| The following reproducer triggers the problem and explains how/why it |
| happens in its comments: |
| |
| $ cat test-send-unlink.sh |
| #!/bin/bash |
| |
| DEV=/dev/sdi |
| MNT=/mnt/sdi |
| |
| mkfs.btrfs -f $DEV >/dev/null |
| mount $DEV $MNT |
| |
| # Create our test files and directory. Inode 259 (file3) has two hard |
| # links. |
| touch $MNT/file1 |
| touch $MNT/file2 |
| touch $MNT/file3 |
| |
| mkdir $MNT/A |
| ln $MNT/file3 $MNT/A/hard_link |
| |
| # Filesystem looks like: |
| # |
| # . (ino 256) |
| # |----- file1 (ino 257) |
| # |----- file2 (ino 258) |
| # |----- file3 (ino 259) |
| # |----- A/ (ino 260) |
| # |---- hard_link (ino 259) |
| # |
| |
| # Now create the base snapshot, which is going to be the parent snapshot |
| # for a later incremental send. |
| btrfs subvolume snapshot -r $MNT $MNT/snap1 |
| btrfs send -f /tmp/snap1.send $MNT/snap1 |
| |
| # Move inode 257 into directory inode 260. This results in computing the |
| # path for inode 260 as "/A" and caching it. |
| mv $MNT/file1 $MNT/A/file1 |
| |
| # Move inode 258 (file2) into directory inode 260, with a name of |
| # "hard_link", moving first inode 259 away since it currently has that |
| # location and name. |
| mv $MNT/A/hard_link $MNT/tmp |
| mv $MNT/file2 $MNT/A/hard_link |
| |
| # Now rename inode 260 to something else (B for example) and then create |
| # a hard link for inode 258 that has the old name and location of inode |
| # 260 ("/A"). |
| mv $MNT/A $MNT/B |
| ln $MNT/B/hard_link $MNT/A |
| |
| # Filesystem now looks like: |
| # |
| # . (ino 256) |
| # |----- tmp (ino 259) |
| # |----- file3 (ino 259) |
| # |----- B/ (ino 260) |
| # | |---- file1 (ino 257) |
| # | |---- hard_link (ino 258) |
| # | |
| # |----- A (ino 258) |
| |
| # Create another snapshot of our subvolume and use it for an incremental |
| # send. |
| btrfs subvolume snapshot -r $MNT $MNT/snap2 |
| btrfs send -f /tmp/snap2.send -p $MNT/snap1 $MNT/snap2 |
| |
| # Now unmount the filesystem, create a new one, mount it and try to |
| # apply both send streams to recreate both snapshots. |
| umount $DEV |
| |
| mkfs.btrfs -f $DEV >/dev/null |
| |
| mount $DEV $MNT |
| |
| # First add the first snapshot to the new filesystem by applying the |
| # first send stream. |
| btrfs receive -f /tmp/snap1.send $MNT |
| |
| # The incremental receive operation below used to fail with the |
| # following error: |
| # |
| # ERROR: unlink A/hard_link failed: No such file or directory |
| # |
| # This is because when send is processing inode 257, it generates the |
| # path for inode 260 as "/A", since that inode is its parent in the send |
| # snapshot, and caches that path. |
| # |
| # Later when processing inode 258, it first processes its new reference |
| # that has the path of "/A", which results in orphanizing inode 260 |
| # because there is a a path collision. This results in issuing a rename |
| # operation from "/A" to "/o260-6-0". |
| # |
| # Finally when processing the new reference "B/hard_link" for inode 258, |
| # it notices that it collides with inode 259 (not yet processed, because |
| # it has a higher inode number), since that inode has the name |
| # "hard_link" under the directory inode 260. It also checks that inode |
| # 259 has two hardlinks, so it decides to issue a unlink operation for |
| # the name "hard_link" for inode 259. However the path passed to the |
| # unlink operation is "/A/hard_link", which is incorrect since currently |
| # "/A" does not exists, due to the orphanization of inode 260 mentioned |
| # before. The path is incorrect because it was computed and cached |
| # before the orphanization. This results in the receiver to fail with |
| # the above error. |
| btrfs receive -f /tmp/snap2.send $MNT |
| |
| umount $MNT |
| |
| When running the test, it fails like this: |
| |
| $ ./test-send-unlink.sh |
| Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap1' |
| At subvol /mnt/sdi/snap1 |
| Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap2' |
| At subvol /mnt/sdi/snap2 |
| At subvol snap1 |
| At snapshot snap2 |
| ERROR: unlink A/hard_link failed: No such file or directory |
| |
| Fix this by recomputing a path before issuing an unlink operation when |
| processing the new references for the current inode if we previously |
| have orphanized a directory. |
| |
| A test case for fstests will follow soon. |
| |
| CC: stable@vger.kernel.org # 4.4+ |
| Signed-off-by: Filipe Manana <fdmanana@suse.com> |
| Signed-off-by: David Sterba <dsterba@suse.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/btrfs/send.c | 11 +++++++++++ |
| 1 file changed, 11 insertions(+) |
| |
| --- a/fs/btrfs/send.c |
| +++ b/fs/btrfs/send.c |
| @@ -4080,6 +4080,17 @@ static int process_recorded_refs(struct |
| if (ret < 0) |
| goto out; |
| } else { |
| + /* |
| + * If we previously orphanized a directory that |
| + * collided with a new reference that we already |
| + * processed, recompute the current path because |
| + * that directory may be part of the path. |
| + */ |
| + if (orphanized_dir) { |
| + ret = refresh_ref_path(sctx, cur); |
| + if (ret < 0) |
| + goto out; |
| + } |
| ret = send_unlink(sctx, cur->full_path); |
| if (ret < 0) |
| goto out; |
