From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31DD0C83F21 for ; Wed, 30 Aug 2023 19:29:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344077AbjH3T00 (ORCPT ); Wed, 30 Aug 2023 15:26:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343912AbjH3RMo (ORCPT ); Wed, 30 Aug 2023 13:12:44 -0400 Received: from exchange.fintech.ru (exchange.fintech.ru [195.54.195.159]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8787FF; Wed, 30 Aug 2023 10:12:39 -0700 (PDT) Received: from Ex16-01.fintech.ru (10.0.10.18) by exchange.fintech.ru (195.54.195.169) with Microsoft SMTP Server (TLS) id 14.3.498.0; Wed, 30 Aug 2023 20:12:36 +0300 Received: from [192.168.211.130] (10.0.253.138) by Ex16-01.fintech.ru (10.0.10.18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2242.4; Wed, 30 Aug 2023 20:12:36 +0300 Message-ID: <7836783b-458d-4d2a-2de5-4a0118b0941c@fintech.ru> Date: Wed, 30 Aug 2023 10:12:35 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH net] sctp: fix uninit-value in sctp_inq_pop() Content-Language: en-US To: Xin Long CC: Marcelo Ricardo Leitner , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , , , , References: <20230829071334.58083-1-n.zhandarovich@fintech.ru> From: Nikita Zhandarovich In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.0.253.138] X-ClientProxiedBy: Ex16-02.fintech.ru (10.0.10.19) To Ex16-01.fintech.ru (10.0.10.18) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/29/23 13:27, Xin Long wrote: > On Tue, Aug 29, 2023 at 3:14 AM Nikita Zhandarovich > wrote: >> >> Syzbot identified a case [1] of uninitialized memory usage in >> sctp_inq_pop(), specifically in 'ch->length'. >> >> Fix the issue by ensuring that 'ch->length' reflects the size of >> 'sctp_chunkhdr *ch' before accessing it. >> >> [1] >> BUG: KMSAN: uninit-value in sctp_inq_pop+0x1597/0x1910 net/sctp/inqueue.c:205 >> sctp_inq_pop+0x1597/0x1910 net/sctp/inqueue.c:205 >> sctp_assoc_bh_rcv+0x1a7/0xc50 net/sctp/associola.c:997 >> sctp_inq_push+0x23e/0x2b0 net/sctp/inqueue.c:80 >> sctp_backlog_rcv+0x394/0xd80 net/sctp/input.c:331 >> sk_backlog_rcv include/net/sock.h:1115 [inline] >> __release_sock+0x207/0x570 net/core/sock.c:2911 >> release_sock+0x6b/0x1e0 net/core/sock.c:3478 >> sctp_wait_for_connect+0x486/0x810 net/sctp/socket.c:9325 >> sctp_sendmsg_to_asoc+0x1ea7/0x1ee0 net/sctp/socket.c:1884 >> ... >> >> Uninit was stored to memory at: >> sctp_inq_pop+0x151a/0x1910 net/sctp/inqueue.c:201 >> sctp_assoc_bh_rcv+0x1a7/0xc50 net/sctp/associola.c:997 >> sctp_inq_push+0x23e/0x2b0 net/sctp/inqueue.c:80 >> sctp_backlog_rcv+0x394/0xd80 net/sctp/input.c:331 >> sk_backlog_rcv include/net/sock.h:1115 [inline] >> __release_sock+0x207/0x570 net/core/sock.c:2911 >> release_sock+0x6b/0x1e0 net/core/sock.c:3478 >> sctp_wait_for_connect+0x486/0x810 net/sctp/socket.c:9325 >> sctp_sendmsg_to_asoc+0x1ea7/0x1ee0 net/sctp/socket.c:1884 >> ... >> >> Uninit was created at: >> slab_post_alloc_hook+0x12d/0xb60 mm/slab.h:716 >> slab_alloc_node mm/slub.c:3451 [inline] >> __kmem_cache_alloc_node+0x4ff/0x8b0 mm/slub.c:3490 >> __do_kmalloc_node mm/slab_common.c:965 [inline] >> __kmalloc_node_track_caller+0x118/0x3c0 mm/slab_common.c:986 >> kmalloc_reserve+0x248/0x470 net/core/skbuff.c:585 >> __alloc_skb+0x318/0x740 net/core/skbuff.c:654 >> alloc_skb include/linux/skbuff.h:1288 [inline] >> sctp_packet_pack net/sctp/output.c:472 [inline] >> sctp_packet_transmit+0x1729/0x4150 net/sctp/output.c:621 >> sctp_outq_flush_transports net/sctp/outqueue.c:1173 [inline] >> ... >> >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >> Reported-and-tested-by: syzbot+70a42f45e76bede082be@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=70a42f45e76bede082be >> Signed-off-by: Nikita Zhandarovich >> --- >> net/sctp/inqueue.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/net/sctp/inqueue.c b/net/sctp/inqueue.c >> index 7182c5a450fb..98ce9524c87c 100644 >> --- a/net/sctp/inqueue.c >> +++ b/net/sctp/inqueue.c >> @@ -197,6 +197,7 @@ struct sctp_chunk *sctp_inq_pop(struct sctp_inq *queue) >> } >> } >> >> + ch->length = htons(sizeof(*ch)); >> chunk->chunk_hdr = ch; >> chunk->chunk_end = ((__u8 *)ch) + SCTP_PAD4(ntohs(ch->length)); >> skb_pull(chunk->skb, sizeof(*ch)); >> -- >> 2.25.1 >> > Hi, Nikita > > You can't just overwrite "ch->length", "ch" is the header of the received chunk. > if it says ch->length is Uninit, it means either the chunk parsing in > the receiver > is overflow or the format of the chunk created in the sender is incorrect. > > If you can reproduce it stably, I suggest you start from sctp_inq_pop() and > print out the skb info and data in there, and see if it's a normal chunk. > > Thanks. Thank you for your feedback, I'll follow your advice and try to narrow the problem down. With regards, Nikita