Date:   Wed, 13 Feb 2019 12:35:56 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     syzbot <syzbot+7823fa3f3e2d69341ea8@...kaller.appspotmail.com>
Cc:     davem <davem@...emloft.net>, LKML <linux-kernel@...r.kernel.org>,
        linux-sctp@...r.kernel.org,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        network dev <netdev@...r.kernel.org>,
        Neil Horman <nhorman@...driver.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Vlad Yasevich <vyasevich@...il.com>
Subject: Re: KASAN: use-after-free Read in sctp_outq_tail

On Wed, Feb 13, 2019 at 4:00 AM syzbot
<syzbot+7823fa3f3e2d69341ea8@...kaller.appspotmail.com> 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@...kaller.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.


>
> 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+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@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.

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