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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NORMAL_HTTP_TO_IP,NUMERIC_HTTP_ADDR, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A683BC76191 for ; Wed, 24 Jul 2019 12:13:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7EBEE21850 for ; Wed, 24 Jul 2019 12:13:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728080AbfGXMN6 (ORCPT ); Wed, 24 Jul 2019 08:13:58 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:2234 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726578AbfGXMN5 (ORCPT ); Wed, 24 Jul 2019 08:13:57 -0400 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 9643F371BDA4D0488F12; Wed, 24 Jul 2019 20:13:54 +0800 (CST) Received: from [127.0.0.1] (10.177.96.96) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.439.0; Wed, 24 Jul 2019 20:13:56 +0800 Subject: Re: [PATCH 4.4 stable net] net: tcp: Fix use-after-free in tcp_write_xmit To: Greg KH References: <20190724091715.137033-1-maowenan@huawei.com> <20190724110524.GA4472@kroah.com> CC: , , , From: maowenan Message-ID: Date: Wed, 24 Jul 2019 20:13:42 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20190724110524.GA4472@kroah.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.96.96] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/7/24 19:05, Greg KH wrote: > On Wed, Jul 24, 2019 at 05:17:15PM +0800, Mao Wenan wrote: >> There is one report about tcp_write_xmit use-after-free with version 4.4.136: >> >> BUG: KASAN: use-after-free in tcp_skb_pcount include/net/tcp.h:796 [inline] >> BUG: KASAN: use-after-free in tcp_init_tso_segs net/ipv4/tcp_output.c:1619 [inline] >> BUG: KASAN: use-after-free in tcp_write_xmit+0x3fc2/0x4cb0 net/ipv4/tcp_output.c:2056 >> Read of size 2 at addr ffff8801d6fc87b0 by task syz-executor408/4195 >> >> CPU: 0 PID: 4195 Comm: syz-executor408 Not tainted 4.4.136-gfb7e319 #59 >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 >> 0000000000000000 7d8f38ecc03be946 ffff8801d73b7710 ffffffff81e0edad >> ffffea00075bf200 ffff8801d6fc87b0 0000000000000000 ffff8801d6fc87b0 >> dffffc0000000000 ffff8801d73b7748 ffffffff815159b6 ffff8801d6fc87b0 >> Call Trace: >> [] __dump_stack lib/dump_stack.c:15 [inline] >> [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 >> [] print_address_description+0x6c/0x216 mm/kasan/report.c:252 >> [] kasan_report_error mm/kasan/report.c:351 [inline] >> [] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408 >> [] __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:427 >> [] tcp_skb_pcount include/net/tcp.h:796 [inline] >> [] tcp_init_tso_segs net/ipv4/tcp_output.c:1619 [inline] >> [] tcp_write_xmit+0x3fc2/0x4cb0 net/ipv4/tcp_output.c:2056 >> [] __tcp_push_pending_frames+0xa0/0x290 net/ipv4/tcp_output.c:2307 >> [] tcp_send_fin+0x176/0xab0 net/ipv4/tcp_output.c:2883 >> [] tcp_close+0xca0/0xf70 net/ipv4/tcp.c:2112 >> [] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435 >> [] sock_release+0x96/0x1c0 net/socket.c:586 >> [] sock_close+0x16/0x20 net/socket.c:1037 >> [] __fput+0x235/0x6f0 fs/file_table.c:208 >> [] ____fput+0x15/0x20 fs/file_table.c:244 >> [] task_work_run+0x10f/0x190 kernel/task_work.c:115 >> [] exit_task_work include/linux/task_work.h:21 [inline] >> [] do_exit+0x9e5/0x26b0 kernel/exit.c:759 >> [] do_group_exit+0x111/0x330 kernel/exit.c:889 >> [] get_signal+0x4ec/0x14b0 kernel/signal.c:2321 >> [] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712 >> [] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:248 >> [] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline] >> [] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:348 >> [] int_ret_from_sys_call+0x25/0xa3 >> >> Allocated by task 4194: >> [] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 >> [] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 >> [] set_track mm/kasan/kasan.c:524 [inline] >> [] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616 >> [] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554 >> [] slab_post_alloc_hook mm/slub.c:1349 [inline] >> [] slab_alloc_node mm/slub.c:2615 [inline] >> [] slab_alloc mm/slub.c:2623 [inline] >> [] kmem_cache_alloc+0xbe/0x2a0 mm/slub.c:2628 >> [] kmem_cache_alloc_node include/linux/slab.h:350 [inline] >> [] __alloc_skb+0xe6/0x600 net/core/skbuff.c:218 >> [] alloc_skb_fclone include/linux/skbuff.h:856 [inline] >> [] sk_stream_alloc_skb+0xa3/0x5d0 net/ipv4/tcp.c:833 >> [] tcp_sendmsg+0xd34/0x2b00 net/ipv4/tcp.c:1178 >> [] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755 >> [] sock_sendmsg_nosec net/socket.c:625 [inline] >> [] sock_sendmsg+0xcc/0x110 net/socket.c:635 >> [] SYSC_sendto+0x21c/0x370 net/socket.c:1665 >> [] SyS_sendto+0x40/0x50 net/socket.c:1633 >> [] entry_SYSCALL_64_fastpath+0x22/0x9e >> >> Freed by task 4194: >> [] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63 >> [] save_stack+0x43/0xd0 mm/kasan/kasan.c:512 >> [] set_track mm/kasan/kasan.c:524 [inline] >> [] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589 >> [] slab_free_hook mm/slub.c:1383 [inline] >> [] slab_free_freelist_hook mm/slub.c:1405 [inline] >> [] slab_free mm/slub.c:2859 [inline] >> [] kmem_cache_free+0xbe/0x340 mm/slub.c:2881 >> [] kfree_skbmem+0xcf/0x100 net/core/skbuff.c:635 >> [] __kfree_skb+0x1d/0x20 net/core/skbuff.c:676 >> [] sk_wmem_free_skb include/net/sock.h:1447 [inline] >> [] tcp_write_queue_purge include/net/tcp.h:1460 [inline] >> [] tcp_connect_init net/ipv4/tcp_output.c:3122 [inline] >> [] tcp_connect+0xb24/0x30c0 net/ipv4/tcp_output.c:3261 >> [] tcp_v4_connect+0xf31/0x1890 net/ipv4/tcp_ipv4.c:246 >> [] __inet_stream_connect+0x2a9/0xc30 net/ipv4/af_inet.c:615 >> [] inet_stream_connect+0x55/0xa0 net/ipv4/af_inet.c:676 >> [] SYSC_connect+0x1b8/0x300 net/socket.c:1557 >> [] SyS_connect+0x24/0x30 net/socket.c:1538 >> [] entry_SYSCALL_64_fastpath+0x22/0x9e >> >> Syzkaller reproducer(): >> r0 = socket$packet(0x11, 0x3, 0x300) >> r1 = socket$inet_tcp(0x2, 0x1, 0x0) >> bind$inet(r1, &(0x7f0000000300)={0x2, 0x4e21, @multicast1}, 0x10) >> connect$inet(r1, &(0x7f0000000140)={0x2, 0x1000004e21, @loopback}, 0x10) >> recvmmsg(r1, &(0x7f0000001e40)=[{{0x0, 0x0, &(0x7f0000000100)=[{&(0x7f00000005c0)=""/88, 0x58}], 0x1}}], 0x1, 0x40000000, 0x0) >> sendto$inet(r1, &(0x7f0000000000)="e2f7ad5b661c761edf", 0x9, 0x8080, 0x0, 0x0) >> r2 = fcntl$dupfd(r1, 0x0, r0) >> connect$unix(r2, &(0x7f00000001c0)=@file={0x0, './file0\x00'}, 0x6e) >> >> C repro link: https://syzkaller.appspot.com/text?tag=ReproC&x=14db474f800000 >> >> This is because when tcp_connect_init call tcp_write_queue_purge, it will >> kfree all the skb in the write_queue, but the sk->sk_send_head forget to set NULL, >> then tcp_write_xmit try to send skb, which has freed in tcp_write_queue_purge, UAF happens. >> >> Signed-off-by: Mao Wenan >> --- >> include/net/tcp.h | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/include/net/tcp.h b/include/net/tcp.h >> index bf8a0dae977a..8f8aace28cf8 100644 >> --- a/include/net/tcp.h >> +++ b/include/net/tcp.h >> @@ -1457,6 +1457,7 @@ static inline void tcp_write_queue_purge(struct sock *sk) >> >> while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL) >> sk_wmem_free_skb(sk, skb); >> + sk->sk_send_head = NULL; >> sk_mem_reclaim(sk); >> tcp_clear_all_retrans_hints(tcp_sk(sk)); >> inet_csk(sk)->icsk_backoff = 0; > > Does this corrispond with a specific commit that is already in Linus's > tree? If not, why, did we change/mess something up when doing > backports, or is the code just that different? > > Also, is this needed in 4.9.y, 4.14.y, 4.19.y, and/or 5.2.y? Why just > 4.4.y? Is it the commit 75c119afe14f? It does not use sk_send_head to indicate whether it has skb to be sent. commit 75c119afe14f74b4dd967d75ed9f57ab6c0ef045 Author: Eric Dumazet Date: Thu Oct 5 22:21:27 2017 -0700 tcp: implement rb-tree based retransmit queue static inline struct sk_buff *tcp_send_head(const struct sock *sk) { - return sk->sk_send_head; + return skb_peek(&sk->sk_write_queue); } > > thanks, > > greg k-h > > . >