afs: Fix missing cursor clearance
afs_select_fileserver() ends the address cursor it is using in the case in
which we get some sort of network error and run out of addresses to iterate
through, before it jumps to try the next server. This also needs to be
done when the server aborts with some sort of error that means we should
try the next server.
Fix this by:
(1) Move the iterate_address afs_end_cursor() call to the next_server
case.
(2) End the cursor in the failed case.
(3) Make afs_end_cursor() clear the ->begun flag and ->addr pointer in the
address cursor.
(4) Make afs_end_cursor() able to be called on an already cleared cursor.
Without this, something like the following oops may occur:
AFS: Assertion failed
18446612134397189888 == 0 is false
0xffff88007c279f00 == 0x0 is false
------------[ cut here ]------------
kernel BUG at fs/afs/rotate.c:360!
RIP: 0010:afs_select_fileserver+0x79b/0xa30 [kafs]
Call Trace:
afs_statfs+0xcc/0x180 [kafs]
? p9_client_statfs+0x9e/0x110 [9pnet]
? _cond_resched+0x19/0x40
statfs_by_dentry+0x6d/0x90
vfs_statfs+0x1b/0xc0
user_statfs+0x4b/0x80
SYSC_statfs+0x15/0x30
SyS_statfs+0xe/0x10
entry_SYSCALL_64_fastpath+0x20/0x83
Fixes: d2ddc776a458 ("afs: Overhaul volume and server record caching and fileserver rotation")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: stable@vger.kernel.org
diff --git a/fs/afs/addr_list.c b/fs/afs/addr_list.c
index a537368..fd9f28b 100644
--- a/fs/afs/addr_list.c
+++ b/fs/afs/addr_list.c
@@ -332,11 +332,18 @@
*/
int afs_end_cursor(struct afs_addr_cursor *ac)
{
- if (ac->responded && ac->index != ac->start)
- WRITE_ONCE(ac->alist->index, ac->index);
+ struct afs_addr_list *alist;
- afs_put_addrlist(ac->alist);
+ alist = ac->alist;
+ if (alist) {
+ if (ac->responded && ac->index != ac->start)
+ WRITE_ONCE(alist->index, ac->index);
+ afs_put_addrlist(alist);
+ }
+
+ ac->addr = NULL;
ac->alist = NULL;
+ ac->begun = false;
return ac->error;
}