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Wed, 13 Feb 2019 05:52:01 -0800 (PST) Received: from localhost.localdomain ([2001:1284:f019:3a5b:b662:7c1a:9012:e865]) by smtp.gmail.com with ESMTPSA id b77sm28461003qka.5.2019.02.13.05.52.00 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 13 Feb 2019 05:52:00 -0800 (PST) Received: by localhost.localdomain (Postfix, from userid 1000) id 1EDFD180BCF; Wed, 13 Feb 2019 11:51:58 -0200 (-02) Date: Wed, 13 Feb 2019 11:51:58 -0200 From: Marcelo Ricardo Leitner To: Xin Long Cc: syzbot , davem , LKML , linux-sctp@vger.kernel.org, network dev , Neil Horman , syzkaller-bugs , Vlad Yasevich Subject: Re: KASAN: use-after-free Read in sctp_outq_tail Message-ID: <20190213135157.GJ10665@localhost.localdomain> References: <0000000000002015db0581b71858@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 13, 2019 at 12:35:56PM +0800, Xin Long wrote: > On Wed, Feb 13, 2019 at 4:00 AM syzbot > wrote: > > > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: d4104460aec1 Add linux-next specific files for 20190211 > > git tree: linux-next > > console output: https://syzkaller.appspot.com/x/log.txt?x=14140124c00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=c8a112d3b0d6719b > > dashboard link: https://syzkaller.appspot.com/bug?extid=7823fa3f3e2d69341ea8 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > Unfortunately, I don't have any reproducer for this crash yet. > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+7823fa3f3e2d69341ea8@syzkaller.appspotmail.com > > > > ================================================================== > > BUG: KASAN: use-after-free in list_add_tail include/linux/list.h:93 [inline] > > BUG: KASAN: use-after-free in sctp_outq_tail_data net/sctp/outqueue.c:105 > > [inline] > > BUG: KASAN: use-after-free in sctp_outq_tail+0x816/0x930 > > net/sctp/outqueue.c:313 > > Read of size 8 at addr ffff88807b19a7b8 by task syz-executor.0/30745 > I think https://patchwork.ozlabs.org/patch/1040500/ will fix this. I don't think so. Seems it will switch from use-after-free to NULL deref instead with that patch. > > CPU: 1 PID: 30745 Comm: syz-executor.0 Not tainted 5.0.0-rc5-next-20190211 > > #32 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x172/0x1f0 lib/dump_stack.c:113 > > print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187 > > kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317 > > __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132 > > list_add_tail include/linux/list.h:93 [inline] > > sctp_outq_tail_data net/sctp/outqueue.c:105 [inline] > > sctp_outq_tail+0x816/0x930 net/sctp/outqueue.c:313 > > sctp_cmd_send_msg net/sctp/sm_sideeffect.c:1109 [inline] > > sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1784 [inline] > > sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline] > > sctp_do_sm+0x68e/0x5380 net/sctp/sm_sideeffect.c:1191 > > sctp_primitive_SEND+0xa0/0xd0 net/sctp/primitive.c:178 > > sctp_sendmsg_to_asoc+0xa63/0x17b0 net/sctp/socket.c:1955 sctp_sendmsg_to_asoc() ... if (sinfo->sinfo_stream >= asoc->stream.outcnt) { err = -EINVAL; goto err; } if (unlikely(!SCTP_SO(&asoc->stream, sinfo->sinfo_stream)->ext)) { ... It should have aborted even if an old ->ext was still there because outcnt is correctly updated. So somehow outcnt was wrong here. sctp_stream_init() ... /* Filter out chunks queued on streams that won't exist anymore */ sched->unsched_all(stream); sctp_stream_outq_migrate(stream, NULL, outcnt); <--- [A] sched->sched_all(stream); ret = sctp_stream_alloc_out(stream, outcnt, gfp); <--- [B] if (ret) goto out; stream->outcnt = outcnt; <--- [C] ... We have a problem here because [A] is freeing ->ext, but [B] can fail (ENOMEM), which would lead it to not update outcnt in [C] even after the changes already performed in [A]. It should handle the freeing of ->ext in sctp_stream_alloc_out() instead, or allocate the flexarray earlier (so it can bail out before freeing stuff). > > sctp_sendmsg+0x10a9/0x17e0 net/sctp/socket.c:2113 > > inet_sendmsg+0x147/0x5d0 net/ipv4/af_inet.c:798 > > sock_sendmsg_nosec net/socket.c:621 [inline] > > sock_sendmsg+0xdd/0x130 net/socket.c:631 > > ___sys_sendmsg+0x806/0x930 net/socket.c:2136 > > __sys_sendmsg+0x105/0x1d0 net/socket.c:2174 > > __do_sys_sendmsg net/socket.c:2183 [inline] > > __se_sys_sendmsg net/socket.c:2181 [inline] > > __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2181 > > do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x457e39 > > Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > > RSP: 002b:00007fa9b8630c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e > > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457e39 > > RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003 > > RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa9b86316d4 > > R13: 00000000004c4e2b R14: 00000000004d8ab8 R15: 00000000ffffffff > > > > Allocated by task 30745: > > save_stack+0x45/0xd0 mm/kasan/common.c:75 > > set_track mm/kasan/common.c:87 [inline] > > __kasan_kmalloc mm/kasan/common.c:498 [inline] > > __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:471 > > kasan_kmalloc+0x9/0x10 mm/kasan/common.c:506 > > kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3615 > > kmalloc include/linux/slab.h:548 [inline] > > kzalloc include/linux/slab.h:743 [inline] > > sctp_stream_init_ext+0x51/0x110 net/sctp/stream.c:172 > > sctp_sendmsg_to_asoc+0x1273/0x17b0 net/sctp/socket.c:1896 > > sctp_sendmsg+0x10a9/0x17e0 net/sctp/socket.c:2113 > > inet_sendmsg+0x147/0x5d0 net/ipv4/af_inet.c:798 > > sock_sendmsg_nosec net/socket.c:621 [inline] > > sock_sendmsg+0xdd/0x130 net/socket.c:631 > > ___sys_sendmsg+0x806/0x930 net/socket.c:2136 > > __sys_sendmsg+0x105/0x1d0 net/socket.c:2174 > > __do_sys_sendmsg net/socket.c:2183 [inline] > > __se_sys_sendmsg net/socket.c:2181 [inline] > > __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2181 > > do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > Freed by task 30745: > > save_stack+0x45/0xd0 mm/kasan/common.c:75 > > set_track mm/kasan/common.c:87 [inline] > > __kasan_slab_free+0x102/0x150 mm/kasan/common.c:460 > > kasan_slab_free+0xe/0x10 mm/kasan/common.c:468 > > __cache_free mm/slab.c:3491 [inline] > > kfree+0xcf/0x230 mm/slab.c:3816 > > sctp_stream_outq_migrate+0x3e6/0x540 net/sctp/stream.c:88 > > sctp_stream_init+0xbc/0x410 net/sctp/stream.c:139 > > sctp_process_init+0x21c3/0x2b20 net/sctp/sm_make_chunk.c:2466 > > sctp_cmd_process_init net/sctp/sm_sideeffect.c:682 [inline] > > sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1410 [inline] > > sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline] > > sctp_do_sm+0x3145/0x5380 net/sctp/sm_sideeffect.c:1191 > > sctp_assoc_bh_rcv+0x343/0x660 net/sctp/associola.c:1074 > > sctp_inq_push+0x1ea/0x290 net/sctp/inqueue.c:95 > > sctp_backlog_rcv+0x196/0xbe0 net/sctp/input.c:354 > > sk_backlog_rcv include/net/sock.h:937 [inline] > > __release_sock+0x12e/0x3a0 net/core/sock.c:2379 > > release_sock+0x59/0x1c0 net/core/sock.c:2895 > > sctp_wait_for_connect+0x316/0x540 net/sctp/socket.c:8998 > > sctp_sendmsg_to_asoc+0x13e3/0x17b0 net/sctp/socket.c:1967 > > sctp_sendmsg+0x10a9/0x17e0 net/sctp/socket.c:2113 > > inet_sendmsg+0x147/0x5d0 net/ipv4/af_inet.c:798 > > sock_sendmsg_nosec net/socket.c:621 [inline] > > sock_sendmsg+0xdd/0x130 net/socket.c:631 > > ___sys_sendmsg+0x806/0x930 net/socket.c:2136 > > __sys_sendmsg+0x105/0x1d0 net/socket.c:2174 > > __do_sys_sendmsg net/socket.c:2183 [inline] > > __se_sys_sendmsg net/socket.c:2181 [inline] > > __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2181 > > do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > The buggy address belongs to the object at ffff88807b19a780 > > which belongs to the cache kmalloc-96 of size 96 > > The buggy address is located 56 bytes inside of > > 96-byte region [ffff88807b19a780, ffff88807b19a7e0) > > The buggy address belongs to the page: > > page:ffffea0001ec6680 count:1 mapcount:0 mapping:ffff88812c3f04c0 > > index:0xffff88807b19a800 > > flags: 0x1fffc0000000200(slab) > > raw: 01fffc0000000200 ffffea000262acc8 ffffea0001448348 ffff88812c3f04c0 > > raw: ffff88807b19a800 ffff88807b19a000 000000010000001d 0000000000000000 > > page dumped because: kasan: bad access detected > > > > Memory state around the buggy address: > > ffff88807b19a680: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > > ffff88807b19a700: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > > > ffff88807b19a780: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > > ^ > > ffff88807b19a800: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > > ffff88807b19a880: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > > ================================================================== > > > > > > --- > > This bug is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@googlegroups.com. > > > > syzbot will keep track of this bug report. See: > > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with > > syzbot. >