Re: KASAN: use-after-free Read in sctp_hash_transport

[Xin Long]

On Mon, Nov 19, 2018 at 4:23 AM syzbot
<syzbot+0b05d8aa7cb185107483@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    e119a369b0f1 Merge branch 'SMSC95xx-driver-updates'
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=124f5f7b400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d86f24333880b605
> dashboard link: https://syzkaller.appspot.com/bug?extid=0b05d8aa7cb185107483
> compiler:       gcc (GCC) 8.0.1 20180413 (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+0b05d8aa7cb185107483@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: use-after-free in sctp_hash_transport+0x803/0x810
> net/sctp/input.c:958
> Read of size 8 at addr ffff8881c6b98cb0 by task syz-executor5/3552
>
> CPU: 0 PID: 3552 Comm: syz-executor5 Not tainted 4.20.0-rc2+ #299
> 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+0x244/0x39d lib/dump_stack.c:113
>   print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
>   kasan_report_error mm/kasan/report.c:354 [inline]
>   kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>   sctp_hash_transport+0x803/0x810 net/sctp/input.c:958
Caused by:
commit cd2b708750582e327789d8fb07c6eb5f79f7759f
Author: Xin Long <lucien.xin@xxxxxxxxx>
Date:   Fri Feb 17 16:35:24 2017 +0800

    sctp: check duplicate node before inserting a new transport

A same fix is needed as:
commit bab1be79a5169ac748d8292b20c86d874022d7ba
Author: Xin Long <lucien.xin@xxxxxxxxx>
Date:   Mon Aug 27 18:38:31 2018 +0800

    sctp: hold transport before accessing its asoc in sctp_transport_get_next


>   sctp_assoc_add_peer+0xa21/0x10d0 net/sctp/associola.c:724
>   sctp_sendmsg_new_asoc+0x5da/0x11f0 net/sctp/socket.c:1757
>   sctp_sendmsg+0x18a5/0x1da0 net/sctp/socket.c:2086
>   inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
>   sock_sendmsg_nosec net/socket.c:621 [inline]
>   sock_sendmsg+0xd5/0x120 net/socket.c:631
>   ___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
>   __sys_sendmsg+0x11d/0x280 net/socket.c:2154
>   __do_sys_sendmsg net/socket.c:2163 [inline]
>   __se_sys_sendmsg net/socket.c:2161 [inline]
>   __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457569
> Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f45462c7c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
> RDX: 0000000000000000 RSI: 000000002001afc8 RDI: 0000000000000005
> RBP: 000000000072c0e0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f45462c86d4
> R13: 00000000004c381e R14: 00000000004d59e8 R15: 00000000ffffffff
>
> Allocated by task 3509:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
>   kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
>   kmalloc include/linux/slab.h:546 [inline]
>   kzalloc include/linux/slab.h:741 [inline]
>   sctp_association_new+0x14e/0x2290 net/sctp/associola.c:311
>   sctp_sendmsg_new_asoc+0x39c/0x11f0 net/sctp/socket.c:1723
>   sctp_sendmsg+0x18a5/0x1da0 net/sctp/socket.c:2086
>   inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
>   sock_sendmsg_nosec net/socket.c:621 [inline]
>   sock_sendmsg+0xd5/0x120 net/socket.c:631
>   ___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
>   __sys_sendmsg+0x11d/0x280 net/socket.c:2154
>   __do_sys_sendmsg net/socket.c:2163 [inline]
>   __se_sys_sendmsg net/socket.c:2161 [inline]
>   __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 3552:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
>   kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>   __cache_free mm/slab.c:3498 [inline]
>   kfree+0xcf/0x230 mm/slab.c:3817
>   sctp_association_destroy net/sctp/associola.c:437 [inline]
>   sctp_association_put+0x264/0x350 net/sctp/associola.c:889
>   sctp_transport_destroy net/sctp/transport.c:180 [inline]
>   sctp_transport_put+0x186/0x1f0 net/sctp/transport.c:340
>   sctp_hash_cmp+0x1ef/0x260 net/sctp/input.c:901
>   __rhashtable_lookup.isra.24.constprop.29+0x3b6/0x7d0
> include/linux/rhashtable.h:483
>   rhltable_lookup include/linux/rhashtable.h:566 [inline]
>   sctp_hash_transport+0x2f6/0x810 net/sctp/input.c:954
>   sctp_assoc_add_peer+0xa21/0x10d0 net/sctp/associola.c:724
>   sctp_sendmsg_new_asoc+0x5da/0x11f0 net/sctp/socket.c:1757
>   sctp_sendmsg+0x18a5/0x1da0 net/sctp/socket.c:2086
>   inet_sendmsg+0x1a1/0x690 net/ipv4/af_inet.c:798
>   sock_sendmsg_nosec net/socket.c:621 [inline]
>   sock_sendmsg+0xd5/0x120 net/socket.c:631
>   ___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
>   __sys_sendmsg+0x11d/0x280 net/socket.c:2154
>   __do_sys_sendmsg net/socket.c:2163 [inline]
>   __se_sys_sendmsg net/socket.c:2161 [inline]
>   __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8881c6b98c00
>   which belongs to the cache kmalloc-4k of size 4096
> The buggy address is located 176 bytes inside of
>   4096-byte region [ffff8881c6b98c00, ffff8881c6b99c00)
> The buggy address belongs to the page:
> page:ffffea00071ae600 count:1 mapcount:0 mapping:ffff8881da800dc0 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000010200(slab|head)
> raw: 02fffc0000010200 ffffea0007175888 ffffea0006421308 ffff8881da800dc0
> raw: 0000000000000000 ffff8881c6b98c00 0000000100000001 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8881c6b98b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff8881c6b98c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8881c6b98c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                       ^
>   ffff8881c6b98d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881c6b98d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> 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@xxxxxxxxxxxxxxxxx
>
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