linux-kernel - Re: [syzbot] [rdma?] [s390?] [net?] KASAN: null-ptr-deref Read in smc_tcp_syn_recv

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Message-ID: <20250630002712.2109-1-hdanton@sina.com>
Date: Mon, 30 Jun 2025 08:27:11 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+827ae2bfb3a3529333e9@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [rdma?] [s390?] [net?] KASAN: null-ptr-deref Read in smc_tcp_syn_recv_sock

> Date: Mon, 31 Mar 2025 13:23:20 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    850925a8133c Merge tag '9p-for-6.12-rc5' of https://github..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1227aa87980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=17c0d505695d6b0
> dashboard link: https://syzkaller.appspot.com/bug?extid=827ae2bfb3a3529333e9
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15489230580000

#syz test upstream   master

--- x/net/smc/af_smc.c
+++ y/net/smc/af_smc.c
@@ -127,6 +127,8 @@ static struct sock *smc_tcp_syn_recv_soc
 	struct sock *child;
 
 	smc = smc_clcsock_user_data(sk);
+	if (!smc)
+		goto drop;
 
 	if (READ_ONCE(sk->sk_ack_backlog) + atomic_read(&smc->queued_smc_hs) >
 				sk->sk_max_ack_backlog)
--