Re: [syzbot] [syzbot] [bpf?] [trace?] WARNING in format_decode (3)

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Subject: [syzbot] [bpf?] [trace?] WARNING in format_decode (3)
Author: eadavis@xxxxxx

please test unsupported %? in format string

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git 76df934c6d5f
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index c9fdcc5cdce1..78258a822a5c 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -845,6 +845,9 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb)
 {
 	struct qdisc_skb_cb *cb = (struct qdisc_skb_cb *)skb->cb;
 
+	if (!skb->len)
+		return -EINVAL;
+
 	if (!__skb)
 		return 0;