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

[Hillf Danton]

> Date: Sun, 15 Feb 2026 12:21:29 -0800	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a040afa3bca4 gve: fix probe failure if clock read fails
> git tree:       net
> console output: https://syzkaller.appspot.com/x/log.txt?x=165bf05a580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e3161cabe5a361ff
> dashboard link: https://syzkaller.appspot.com/bug?extid=9307c991a6d07ce6e6d8
> compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13dd245a580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16ecdb2a580000

#syz test

--- x/net/core/skmsg.c
+++ y/net/core/skmsg.c
@@ -500,7 +500,13 @@ out:
 int sk_msg_recvmsg(struct sock *sk, struct sk_psock *psock, struct msghdr *msg,
 		   int len, int flags)
 {
-	return __sk_msg_recvmsg(sk, psock, msg, len, flags, NULL);
+	static DEFINE_MUTEX(lk);
+	int rc;
+
+	mutex_lock(&lk);
+	rc = __sk_msg_recvmsg(sk, psock, msg, len, flags, NULL);
+	mutex_unlock(&lk);
+	return rc;
 }
 EXPORT_SYMBOL_GPL(sk_msg_recvmsg);
 
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