This is a note to let you know that I've just added the patch titled afs: Fix dynamic root getattr to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: afs-fix-dynamic-root-getattr.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit e6b94a0c967a03017efa1ba9611ab01c0b55e035 Author: David Howells <dhowells@xxxxxxxxxx> Date: Tue Jun 21 15:59:57 2022 +0100 afs: Fix dynamic root getattr [ Upstream commit cb78d1b5efffe4cf97e16766329dd7358aed3deb ] The recent patch to make afs_getattr consult the server didn't account for the pseudo-inodes employed by the dynamic root-type afs superblock not having a volume or a server to access, and thus an oops occurs if such a directory is stat'd. Fix this by checking to see if the vnode->volume pointer actually points anywhere before following it in afs_getattr(). This can be tested by stat'ing a directory in /afs. It may be sufficient just to do "ls /afs" and the oops looks something like: BUG: kernel NULL pointer dereference, address: 0000000000000020 ... RIP: 0010:afs_getattr+0x8b/0x14b ... Call Trace: <TASK> vfs_statx+0x79/0xf5 vfs_fstatat+0x49/0x62 Fixes: 2aeb8c86d499 ("afs: Fix afs_getattr() to refetch file status if callback break occurred") Reported-by: Marc Dionne <marc.dionne@xxxxxxxxxxxx> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> Reviewed-by: Marc Dionne <marc.dionne@xxxxxxxxxxxx> Tested-by: Marc Dionne <marc.dionne@xxxxxxxxxxxx> cc: linux-afs@xxxxxxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/165408450783.1031787.7941404776393751186.stgit@xxxxxxxxxxxxxxxxxxxxxx/ Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/afs/inode.c b/fs/afs/inode.c index 90eac3ec01cb..622363af4c1b 100644 --- a/fs/afs/inode.c +++ b/fs/afs/inode.c @@ -739,7 +739,8 @@ int afs_getattr(const struct path *path, struct kstat *stat, _enter("{ ino=%lu v=%u }", inode->i_ino, inode->i_generation); - if (!(query_flags & AT_STATX_DONT_SYNC) && + if (vnode->volume && + !(query_flags & AT_STATX_DONT_SYNC) && !test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) { key = afs_request_key(vnode->volume->cell); if (IS_ERR(key))