From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B051936B06F for ; Wed, 1 Apr 2026 11:13:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775042011; cv=none; b=qwjNbmQ6vvUMh81OxCz3gbwxGbPNztWi0LQpAIpqlGG4s8eIu9fTuvKfVFBSZleWqjOtHMzpEORTeDlJ2E2s0pAVnnzMPJitXkxjHlU2tHDoI0Yxykhn4gWnJOy75/omi4Q1+EdiDUiZx3cmvRbyaRSg5K/qBmKOMJhfhZQJ/9A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775042011; c=relaxed/simple; bh=+EMaqmV5IGyRb6aXl8/mlfL+Ehdt6ysva3usNERfTSI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rmEa7mr6FwW/yUwZcZejnV9WxG+hVJUpgnFYPXpDeLrVlRqmCXAAPM0qp09pIKdscKB4XAhzOMvZU652O+cDxhdJS/71Q19hjROg9K5PkmZAaZDf+uBEO6lpVBexxASeR5/5ddINvoQPclminxlWMGdGEwf/vheQObsRW8zlVGY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=HKWUgFTj; arc=none smtp.client-ip=91.218.175.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="HKWUgFTj" Message-ID: <0a06dbbe-1039-48dc-8fa1-331dac63559c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1775042007; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UCdKZSxuAD+d/u0f+cnJAQd8hizdkeJxdxVPMULokRQ=; b=HKWUgFTjS42Gua+FSdX6+neyu9OP/spCiUK9iyVwSNKQNsZS7qJnpGTiSBU3DVFSSfA6/+ Y5kYGafC1umHXuY9uPEUNHTj98XiHTK/yr7Moc51ZQdsZSxKthTZxmanFg+fr1/Zc4ZpbY aQU3MHcX7LNAnQwiw8B9ixUvzujKr4g= Date: Wed, 1 Apr 2026 19:13:17 +0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v1 bpf] sockmap: Fix use-after-free of sk->sk_socket in sk_psock_verdict_data_ready(). To: Kuniyuki Iwashima , John Fastabend , Jakub Sitnicki , Martin KaFai Lau , Alexei Starovoitov , Cong Wang Cc: Kuniyuki Iwashima , bpf@vger.kernel.org, syzbot+2184232f07e3677fbaef@syzkaller.appspotmail.com References: <20260401005418.2452999-1-kuniyu@google.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Jiayuan Chen In-Reply-To: <20260401005418.2452999-1-kuniyu@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 4/1/26 8:54 AM, Kuniyuki Iwashima wrote: > syzbot reported use-after-free of AF_UNIX socket's sk->sk_socket > in sk_psock_verdict_data_ready(). [0] > > In unix_stream_sendmsg(), the peer socket's ->sk_data_ready() is > called after dropping its unix_state_lock(). > > Although the sender socket holds the peer's refcount, it does not > prevent the peer's sock_orphan(), and the peer's sk_socket might > be freed after one RCU grace period. > > Let's fetch the peer's sk->sk_socket and sk->sk_socket->ops under > RCU in sk_psock_verdict_data_ready(). > > [0]: > BUG: KASAN: slab-use-after-free in sk_psock_verdict_data_ready+0xec/0x590 net/core/skmsg.c:1278 > Read of size 8 at addr ffff8880594da860 by task syz.4.1842/11013 > > CPU: 1 UID: 0 PID: 11013 Comm: syz.4.1842 Not tainted syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 > Call Trace: > > dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 > print_address_description mm/kasan/report.c:378 [inline] > print_report+0xba/0x230 mm/kasan/report.c:482 > kasan_report+0x117/0x150 mm/kasan/report.c:595 > sk_psock_verdict_data_ready+0xec/0x590 net/core/skmsg.c:1278 > unix_stream_sendmsg+0x8a3/0xe80 net/unix/af_unix.c:2482 > sock_sendmsg_nosec net/socket.c:721 [inline] > __sock_sendmsg net/socket.c:736 [inline] > ____sys_sendmsg+0x972/0x9f0 net/socket.c:2585 > ___sys_sendmsg+0x2a5/0x360 net/socket.c:2639 > __sys_sendmsg net/socket.c:2671 [inline] > __do_sys_sendmsg net/socket.c:2676 [inline] > __se_sys_sendmsg net/socket.c:2674 [inline] > __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2674 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7facf899c819 > Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007facf9827028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e > RAX: ffffffffffffffda RBX: 00007facf8c15fa0 RCX: 00007facf899c819 > RDX: 0000000000000000 RSI: 0000200000000500 RDI: 0000000000000004 > RBP: 00007facf8a32c91 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007facf8c16038 R14: 00007facf8c15fa0 R15: 00007ffd41b01c78 > [...] > > Fixes: c63829182c37 ("af_unix: Implement ->psock_update_sk_prot()") > Reported-by: syzbot+2184232f07e3677fbaef@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/bpf/69cc6b9f.a70a0220.128fd0.004b.GAE@google.com/ > Signed-off-by: Kuniyuki Iwashima Reviewed-by: Jiayuan Chen > --- > net/core/skmsg.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/net/core/skmsg.c b/net/core/skmsg.c > index 3261793abe83..6187a83bd741 100644 > --- a/net/core/skmsg.c > +++ b/net/core/skmsg.c > @@ -1267,17 +1267,20 @@ static int sk_psock_verdict_recv(struct sock *sk, struct sk_buff *skb) > > static void sk_psock_verdict_data_ready(struct sock *sk) > { > - struct socket *sock = sk->sk_socket; > - const struct proto_ops *ops; > + const struct proto_ops *ops = NULL; > + struct socket *sock; > int copied; > > trace_sk_data_ready(sk); > > - if (unlikely(!sock)) > - return; > - ops = READ_ONCE(sock->ops); > + rcu_read_lock(); > + sock = READ_ONCE(sk->sk_socket); > + if (likely(sock)) > + ops = READ_ONCE(sock->ops); > + rcu_read_unlock(); > if (!ops || !ops->read_skb) > return; > + > copied = ops->read_skb(sk, sk_psock_verdict_recv); > if (copied >= 0) { > struct sk_psock *psock;