Re: [syzbot] [net?] KASAN: slab-use-after-free Read in unix_del_edges

[Hillf Danton]

On Fri, 19 Apr 2024 02:39:21 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    7b4f2bc91c15 Add linux-next specific files for 20240418
> git tree:       linux-next
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=128b1d53180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git  7b4f2bc91c15

--- x/net/unix/garbage.c
+++ y/net/unix/garbage.c
@@ -205,6 +205,7 @@ void unix_add_edges(struct scm_fp_list *
 		edge = fpl->edges + i++;
 		edge->predecessor = inflight;
 		edge->successor = receiver;
+		sock_hold((struct sock *)receiver);
 
 		unix_add_edge(fpl, edge);
 	} while (i < fpl->count_unix);
@@ -225,6 +226,7 @@ void unix_del_edges(struct scm_fp_list *
 {
 	struct unix_sock *receiver;
 	int i = 0;
+	int j;
 
 	spin_lock(&unix_gc_lock);
 
@@ -246,6 +248,12 @@ out:
 	spin_unlock(&unix_gc_lock);
 
 	fpl->inflight = false;
+
+	for (j = 0; j < i; j++) {
+		struct unix_edge *edge = fpl->edges + j;
+
+		sock_put((struct sock *)(edge->successor));
+	}
 }
 
 void unix_update_edges(struct unix_sock *receiver)
--