[PATCH 4.19 17/49] afs: Fix dynamic root getattr
Greg Kroah-Hartman
gregkh at linuxfoundation.org
Thu Jun 30 06:46:30 PDT 2022
From: David Howells <dhowells at redhat.com>
[ 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 at auristor.com>
Signed-off-by: David Howells <dhowells at redhat.com>
Reviewed-by: Marc Dionne <marc.dionne at auristor.com>
Tested-by: Marc Dionne <marc.dionne at auristor.com>
cc: linux-afs at lists.infradead.org
Link: https://lore.kernel.org/r/165408450783.1031787.7941404776393751186.stgit@warthog.procyon.org.uk/
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
fs/afs/inode.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index a12ae3ef8fb4..0983d7e859c8 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -473,7 +473,8 @@ 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))
--
2.35.1
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