Re: [syzbot] [net?] KASAN: slab-use-after-free Write in __xfrm_state_delete

[Edward Adam Davis]

#syz test

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 78fcbb89cf32..137b5b660683 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -929,10 +929,10 @@ int xfrm_state_flush(struct net *net, u8 proto, bool task_valid)
 	err = -ESRCH;
 	for (i = 0; i <= net->xfrm.state_hmask; i++) {
 		struct xfrm_state *x;
-restart:
 		hlist_for_each_entry(x, net->xfrm.state_bydst+i, bydst) {
 			if (!xfrm_state_kern(x) &&
-			    xfrm_id_proto_match(x->id.proto, proto)) {
+			    xfrm_id_proto_match(x->id.proto, proto) &&
+			    x->km.state != XFRM_STATE_DEAD) {
 				xfrm_state_hold(x);
 				spin_unlock_bh(&net->xfrm.xfrm_state_lock);
 
@@ -940,11 +940,9 @@ int xfrm_state_flush(struct net *net, u8 proto, bool task_valid)
 				xfrm_audit_state_delete(x, err ? 0 : 1,
 							task_valid);
 				xfrm_state_put(x);
-				if (!err)
-					cnt++;
+				cnt++;
 
 				spin_lock_bh(&net->xfrm.xfrm_state_lock);
-				goto restart;
 			}
 		}
 	}