From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout05.his.huawei.com (canpmsgout05.his.huawei.com [113.46.200.220]) (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 0BABA1F5834; Wed, 10 Dec 2025 02:51:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.220 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765335077; cv=none; b=rGslagdeuJSZYSsGoWaUcgdhGstjOWYc5tdddgLc9pihfmM8b2PnxvMMAl0r4pVcoN8H/Hz+1u1buq3hYZ0v7yinIKm29JdkdqVYRquQdgPHsIVEODuw2oTJgr6E87pmalzokPlPm7cIWpY7RrJCmIkn8PvxkGBwNnsNnFP775s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765335077; c=relaxed/simple; bh=7BFKKARd40imlyNwDlIXyi3Er26XMY84I58PtlrzrGI=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=MI8chQCd2MBTHLKInsKhtxMgQXOdwMF1AW5Z+XWXNVh2oF1q5kkdxSYgscpjOvmZXFIyx2YO/vTOFivjg/O6ctfA9pEJL5DQx4jNp0S1gB/2UcBPDQ2BtYNp/lv1S/KSC8jd9sN1HyLFFeFBy1LMTMXvdblQE3S7bEnlmSu0cUM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=b7s3reex; arc=none smtp.client-ip=113.46.200.220 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="b7s3reex" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=TjRZnlfDIYUED2pEeefYUgZ5sYiaZ3c/W/77ZGjss7Y=; b=b7s3reexsblE7q740k0U11VxT+rR2797XwcXpBk3PmIHIEyzNGLx2dVn3nbzd34/X18K/JN/u bZnH8Bhxy3wyyx51rYKAq9qJiJuvs/V4GW5e0gPLa4SYzaoRybfvJA5jk+n0hsRilF71EcT4weP QQJjkJu9pEPyDVwwplluwMg= Received: from mail.maildlp.com (unknown [172.19.88.105]) by canpmsgout05.his.huawei.com (SkyGuard) with ESMTPS id 4dR0Xl0pKPz12LKh; Wed, 10 Dec 2025 10:48:55 +0800 (CST) Received: from dggpemf500016.china.huawei.com (unknown [7.185.36.197]) by mail.maildlp.com (Postfix) with ESMTPS id 093EB1402CF; Wed, 10 Dec 2025 10:51:13 +0800 (CST) Received: from [10.174.177.19] (10.174.177.19) by dggpemf500016.china.huawei.com (7.185.36.197) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 10 Dec 2025 10:51:11 +0800 Message-ID: <5d5a0cf3-e085-4921-b340-b84446526985@huawei.com> Date: Wed, 10 Dec 2025 10:51:11 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net] net/handshake: Fix null-ptr-deref in handshake_complete() To: Simon Horman , Chuck Lever CC: , , , , , , , , , , References: <20251209115852.3827876-1-wangliang74@huawei.com> From: Wang Liang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To dggpemf500016.china.huawei.com (7.185.36.197) 在 2025/12/10 2:06, Simon Horman 写道: > On Tue, Dec 09, 2025 at 07:58:52PM +0800, Wang Liang wrote: >> A null pointer dereference in handshake_complete() was observed [1]. >> >> When handshake_req_next() return NULL in handshake_nl_accept_doit(), >> function handshake_complete() will be called unexpectedly which triggers >> this crash. Fix it by goto out_status when req is NULL. >> >> [1] >> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] SMP KASAN PTI >> RIP: 0010:handshake_complete+0x36/0x2b0 net/handshake/request.c:288 >> Call Trace: >> >> handshake_nl_accept_doit+0x32d/0x7e0 net/handshake/netlink.c:129 >> genl_family_rcv_msg_doit+0x204/0x300 net/netlink/genetlink.c:1115 >> genl_family_rcv_msg+0x436/0x670 net/netlink/genetlink.c:1195 >> genl_rcv_msg+0xcc/0x170 net/netlink/genetlink.c:1210 >> netlink_rcv_skb+0x14c/0x430 net/netlink/af_netlink.c:2550 >> genl_rcv+0x2d/0x40 net/netlink/genetlink.c:1219 >> netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] >> netlink_unicast+0x878/0xb20 net/netlink/af_netlink.c:1344 >> netlink_sendmsg+0x897/0xd70 net/netlink/af_netlink.c:1894 >> sock_sendmsg_nosec net/socket.c:727 [inline] >> __sock_sendmsg net/socket.c:742 [inline] >> ____sys_sendmsg+0xa39/0xbf0 net/socket.c:2592 >> ___sys_sendmsg+0x121/0x1c0 net/socket.c:2646 >> __sys_sendmsg+0x155/0x200 net/socket.c:2678 >> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] >> do_syscall_64+0x5f/0x350 arch/x86/entry/syscall_64.c:94 >> entry_SYSCALL_64_after_hwframe+0x76/0x7e >> >> >> Fixes: fe67b063f687 ("net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE()") >> Signed-off-by: Wang Liang >> --- >> net/handshake/netlink.c | 35 ++++++++++++++++++----------------- >> 1 file changed, 18 insertions(+), 17 deletions(-) >> >> diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c >> index 1d33a4675a48..cdaea8b8d004 100644 >> --- a/net/handshake/netlink.c >> +++ b/net/handshake/netlink.c >> @@ -106,25 +106,26 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info) >> >> err = -EAGAIN; >> req = handshake_req_next(hn, class); >> - if (req) { >> - sock = req->hr_sk->sk_socket; >> - >> - FD_PREPARE(fdf, O_CLOEXEC, sock->file); >> - if (fdf.err) { >> - err = fdf.err; >> - goto out_complete; >> - } >> - >> - get_file(sock->file); /* FD_PREPARE() consumes a reference. */ >> - err = req->hr_proto->hp_accept(req, info, fd_prepare_fd(fdf)); >> - if (err) >> - goto out_complete; /* Automatic cleanup handles fput */ >> - >> - trace_handshake_cmd_accept(net, req, req->hr_sk, fd_prepare_fd(fdf)); >> - fd_publish(fdf); >> - return 0; >> + if (!req) >> + goto out_status; >> + >> + sock = req->hr_sk->sk_socket; >> + >> + FD_PREPARE(fdf, O_CLOEXEC, sock->file); >> + if (fdf.err) { >> + err = fdf.err; >> + goto out_complete; >> } >> >> + get_file(sock->file); /* FD_PREPARE() consumes a reference. */ >> + err = req->hr_proto->hp_accept(req, info, fd_prepare_fd(fdf)); >> + if (err) >> + goto out_complete; /* Automatic cleanup handles fput */ >> + >> + trace_handshake_cmd_accept(net, req, req->hr_sk, fd_prepare_fd(fdf)); >> + fd_publish(fdf); >> + return 0; >> + >> out_complete: >> handshake_complete(req, -EIO, NULL); >> out_status: > Hi, > > Clang 21.1.7 W=1 builds are rather unhappy about this: > > net/handshake/netlink.c:110:3: error: cannot jump from this goto statement to its label > 110 | goto out_status; > | ^ > net/handshake/netlink.c:114:13: note: jump bypasses initialization of variable with __attribute__((cleanup)) > 114 | FD_PREPARE(fdf, O_CLOEXEC, sock->file); > | ^ > net/handshake/netlink.c:104:3: error: cannot jump from this goto statement to its label > 104 | goto out_status; > | ^ > net/handshake/netlink.c:114:13: note: jump bypasses initialization of variable with __attribute__((cleanup)) > 114 | FD_PREPARE(fdf, O_CLOEXEC, sock->file); > | ^ > net/handshake/netlink.c:100:3: error: cannot jump from this goto statement to its label > 100 | goto out_status; > | ^ > net/handshake/netlink.c:114:13: note: jump bypasses initialization of variable with __attribute__((cleanup)) > 114 | FD_PREPARE(fdf, O_CLOEXEC, sock->file); > | ^ > > My undersatnding of the problem is as follows: > > FD_PREPARE uses __cleanup to call class_fd_prepare_destructor when > resources when fdf goes out of scope. > > Prior to this patch this was when the if (req) block was existed. > Either via return or a goto due to an error. > > Now it is when handshake_nl_accept_doit() itself is exited. > Again via a return or a goto due to error. > > But, importantly, such a goto can now occur before fdf is initialised. > Boom! Thanks for your analysis, you are right! How about adding a null check before calling handshake_complete()? Like: diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index 1d33a4675a48..b989456fc4c5 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -126,7 +126,8 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)         }  out_complete: -       handshake_complete(req, -EIO, NULL); +       if (req) +               handshake_complete(req, -EIO, NULL);  out_status:         trace_handshake_cmd_accept_err(net, req, NULL, err);         return err; ------ Best regards Wang Liang