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: 2aeb8c86d4 ("afs: Fix afs_getattr() to refetch file status if callback break occurred")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/165408450783.1031787.7941404776393751186.stgit@warthog.procyon.org.uk/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
cb78d1b5ef