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@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: syzbot+3538a6a72efa8b059c38@syzkaller.appspotmail.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 44222923c0d11116e05bd07e542cffb90cb9d26f..24ee585d9aafb6c30768f117a9f2023142a00319 100644 (file)
--- 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);