On Thu, Jun 18, 2020 at 04:45:23PM +0200, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 89efda52e6b6930f80f5adda9c3c9edfb1397191 Mon Sep 17 00:00:00 2001
From: Marcos Paulo de Souza <mpdesouza@xxxxxxxx>
Date: Sun, 10 May 2020 23:15:07 -0300
Subject: [PATCH] btrfs: send: emit file capabilities after chown
Whenever a chown is executed, all capabilities of the file being touched
are lost. When doing incremental send with a file with capabilities,
there is a situation where the capability can be lost on the receiving
side. The sequence of actions bellow shows the problem:
$ mount /dev/sda fs1
$ mount /dev/sdb fs2
$ touch fs1/foo.bar
$ setcap cap_sys_nice+ep fs1/foo.bar
$ btrfs subvolume snapshot -r fs1 fs1/snap_init
$ btrfs send fs1/snap_init | btrfs receive fs2
$ chgrp adm fs1/foo.bar
$ setcap cap_sys_nice+ep fs1/foo.bar
$ btrfs subvolume snapshot -r fs1 fs1/snap_complete
$ btrfs subvolume snapshot -r fs1 fs1/snap_incremental
$ btrfs send fs1/snap_complete | btrfs receive fs2
$ btrfs send -p fs1/snap_init fs1/snap_incremental | btrfs receive fs2
At this point, only a chown was emitted by "btrfs send" since only the
group was changed. This makes the cap_sys_nice capability to be dropped
from fs2/snap_incremental/foo.bar
To fix that, only emit capabilities after chown is emitted. The current
code first checks for xattrs that are new/changed, emits them, and later
emit the chown. Now, __process_new_xattr skips capabilities, letting
only finish_inode_if_needed to emit them, if they exist, for the inode
being processed.
This behavior was being worked around in "btrfs receive" side by caching
the capability and only applying it after chown. Now, xattrs are only
emmited _after_ chown, making that workaround not needed anymore.
Link: https://github.com/kdave/btrfs-progs/issues/202
CC: stable@xxxxxxxxxxxxxxx # 4.4+
Suggested-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Signed-off-by: Marcos Paulo de Souza <mpdesouza@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
I took 1ec9a1ae1e30 ("Btrfs: fix unreplayable log after snapshot delete
+ parent dir fsync") to work around the conflict.
--
Thanks,
Sasha
