Re: [syzbot] KASAN: use-after-free Read in rxrpc_lookup_local
From: David Howells
Date: Tue Dec 06 2022 - 16:10:36 EST
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git master
rxrpc: Fix NULL deref in rxrpc_unuse_local()
Fix rxrpc_unuse_local() to get the debug_id *after* checking to see if
local is NULL.
Fixes: a2cf3264f331 ("rxrpc: Fold __rxrpc_unuse_local() into rxrpc_unuse_local()")
Reported-by: syzbot+3538a6a72efa8b059c38@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Marc Dionne <marc.dionne@xxxxxxxxxxxx>
cc: linux-afs@xxxxxxxxxxxxxxxxxxx
---
net/rxrpc/local_object.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 44222923c0d1..24ee585d9aaf 100644
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -357,10 +357,11 @@ struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local,
*/
void rxrpc_unuse_local(struct rxrpc_local *local, enum rxrpc_local_trace why)
{
- unsigned int debug_id = local->debug_id;
+ unsigned int debug_id;
int r, u;
if (local) {
+ debug_id = local->debug_id;
r = refcount_read(&local->ref);
u = atomic_dec_return(&local->active_users);
trace_rxrpc_local(debug_id, why, r, u);