fs: drop peer group ids under namespace lock

BugLink: https://bugs.launchpad.net/bugs/2016879
commit cb2239c198ad9fbd5aced22cf93e45562da781eb upstream.

When cleaning up peer group ids in the failure path we need to make sure
to hold on to the namespace lock. Otherwise another thread might just
turn the mount from a shared into a non-shared mount concurrently.

Link: https://lore.kernel.org/lkml/00000000000088694505f8132d77@google.com
Fixes: 2a1867219c7b ("fs: add mount_setattr()")
Reported-by: syzbot+8ac3859139c685c4f597@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org # 5.12+
Message-Id: <20230330-vfs-mount_setattr-propagation-fix-v1-1-37548d91533b@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/fs/namespace.c b/fs/namespace.c
index ab467ee5834115b4bea458ebcd5607047d542d95..14fa31f17d77915416929642a964ef92f218571b 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4286,9 +4286,9 @@ out:
        unlock_mount_hash();
 
        if (kattr->propagation) {
-               namespace_unlock();
                if (err)
                        cleanup_group_ids(mnt, NULL);
+               namespace_unlock();
        }
 
        return err;