KASAN: slab-out-of-bounds Read in fl6_update_dst

Status: fixed on 2020/07/17 17:58
Subsystems: net
[Documentation on labels]
Fix commit: bb986a50421a seg6: fix seg6_validate_srh() to avoid slab-out-of-bounds
First crash: 1306d, last: 1261d
Cause bisection: introduced by (bisect log) :
commit 0cb7498f234e4e7d75187a8cae6c7c2053f2488a
Author: Ahmed Abdelsalam <>
Date: Mon May 4 14:42:11 2020 +0000

  seg6: fix SRH processing to comply with RFC8754

Crash: KASAN: slab-out-of-bounds Read in fl6_update_dst (log)
Repro: C syz .config
Discussions (4)
Title Replies (including bot) Last reply
[PATCH 5.7 000/112] 5.7.8-rc1 review 121 (121) 2020/07/09 09:29
[net] seg6: fix seg6_validate_srh() to avoid slab-out-of-bounds 2 (2) 2020/06/04 22:40
[PATCH] seg6: Fix slab-out-of-bounds in fl6_update_dst() 3 (3) 2020/06/02 13:44
KASAN: slab-out-of-bounds Read in fl6_update_dst 0 (2) 2020/05/11 20:01

Sample crash report:
BUG: KASAN: slab-out-of-bounds in fl6_update_dst+0x2bb/0x2c0 net/ipv6/exthdrs.c:1356
Read of size 16 at addr ffff8880a2ebcb68 by task syz-executor865/7114

CPU: 0 PID: 7114 Comm: syz-executor865 Not tainted 5.7.0-rc6-syzkaller #0
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+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:382
 __kasan_report.cold+0x20/0x38 mm/kasan/report.c:511
 kasan_report+0x33/0x50 mm/kasan/common.c:625
 fl6_update_dst+0x2bb/0x2c0 net/ipv6/exthdrs.c:1356
 udpv6_sendmsg+0x1866/0x2b50 net/ipv6/udp.c:1431
 inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:577
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 __sys_sendto+0x220/0x330 net/socket.c:2000
 __do_sys_sendto net/socket.c:2012 [inline]
 __se_sys_sendto net/socket.c:2008 [inline]
 __x64_sys_sendto+0xdd/0x1b0 net/socket.c:2008
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
RIP: 0033:0x446989
Code: e8 0c e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 5b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe98c098da8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00000000006dbc38 RCX: 0000000000446989
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006dbc30 R08: 00000000200001c0 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc3c
R13: 00007fff2890ba2f R14: 00007fe98c0999c0 R15: 0000000000000001

Allocated by task 7108:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc mm/kasan/common.c:495 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:468
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc+0x161/0x7a0 mm/slab.c:3665
 kmalloc include/linux/slab.h:560 [inline]
 sock_kmalloc net/core/sock.c:2166 [inline]
 sock_kmalloc+0xb5/0x100 net/core/sock.c:2157
 ipv6_renew_options+0x274/0x940 net/ipv6/exthdrs.c:1275
 do_ipv6_setsockopt.isra.0+0x2eaf/0x42f0 net/ipv6/ipv6_sockglue.c:435
 ipv6_setsockopt+0xfb/0x180 net/ipv6/ipv6_sockglue.c:949
 udpv6_setsockopt+0x5d/0xa0 net/ipv6/udp.c:1567
 __sys_setsockopt+0x248/0x480 net/socket.c:2132
 __do_sys_setsockopt net/socket.c:2148 [inline]
 __se_sys_setsockopt net/socket.c:2145 [inline]
 __x64_sys_setsockopt+0xba/0x150 net/socket.c:2145
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295

Freed by task 5000:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:456
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x109/0x2b0 mm/slab.c:3757
 kernfs_fop_release+0xe7/0x190 fs/kernfs/file.c:779
 __fput+0x33e/0x880 fs/file_table.c:280
 task_work_run+0xf4/0x1b0 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:305

The buggy address belongs to the object at ffff8880a2ebcb00
 which belongs to the cache kmalloc-128 of size 128
The buggy address is located 104 bytes inside of
 128-byte region [ffff8880a2ebcb00, ffff8880a2ebcb80)
The buggy address belongs to the page:
page:ffffea00028baf00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880a2ebc300
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000256fac8 ffffea000252d808 ffff8880aa000700
raw: ffff8880a2ebc300 ffff8880a2ebc000 0000000100000005 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a2ebca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a2ebca80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a2ebcb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
 ffff8880a2ebcb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a2ebcc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Crashes (43):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/05/23 02:23 upstream 051143e1602d 9682898d .config console log report syz C ci-upstream-kasan-gce-root
2020/05/22 21:42 upstream 051143e1602d 9682898d .config console log report syz C ci-upstream-kasan-gce-smack-root
2020/05/20 21:14 upstream 115a54162a6c 1255f02a .config console log report syz C ci-upstream-kasan-gce-selinux-root
2020/05/20 08:03 upstream 3c9e66568ad4 67fa1f59 .config console log report syz C ci-upstream-kasan-gce-smack-root
2020/05/12 00:23 upstream 152036d1379f 9eb09c40 .config console log report syz C ci-upstream-kasan-gce
2020/05/11 16:14 upstream 2ef96a5bb12b f8f57555 .config console log report syz C ci-upstream-kasan-gce-root
2020/05/11 17:53 net-old e8a1b0efd632 f8f57555 .config console log report syz C ci-upstream-net-this-kasan-gce
2020/05/11 18:06 net-next-old a6f0b26d6a5d f8f57555 .config console log report syz C ci-upstream-net-kasan-gce
2020/05/23 05:48 upstream 051143e1602d 9682898d .config console log report syz ci-upstream-kasan-gce-selinux-root
2020/05/15 20:23 upstream 1ae7efb38854 d7f9fffa .config console log report syz ci-upstream-kasan-gce
2020/05/15 20:17 upstream 1ae7efb38854 d7f9fffa .config console log report syz ci-upstream-kasan-gce-386
2020/05/15 20:22 net-old 207b584d0ab8 d7f9fffa .config console log report syz ci-upstream-net-this-kasan-gce
2020/06/24 21:30 upstream 7ae77150d94d 54566aff .config console log report ci-upstream-kasan-gce
2020/06/18 11:14 upstream 7ae77150d94d d45a4d69 .config console log report ci-upstream-kasan-gce-smack-root
2020/06/09 01:41 upstream 7ae77150d94d 7604bb03 .config console log report ci-upstream-kasan-gce-root
2020/06/07 02:01 upstream 7ae77150d94d e6b89e4e .config console log report ci-upstream-kasan-gce-selinux-root
2020/06/05 11:12 upstream 435faf5c218a 2420d1bc .config console log report ci-upstream-kasan-gce
2020/06/03 20:34 upstream d6f9469a03d8 a5ce5de0 .config console log report ci-upstream-kasan-gce
2020/05/29 06:28 upstream 75caf310d16c d19ed305 .config console log report ci-upstream-kasan-gce
2020/05/28 19:18 upstream b0c3ba31be3e 0d951763 .config console log report ci-upstream-kasan-gce
2020/05/26 00:54 upstream 9cb1fd0efd19 30927cd7 .config console log report ci-upstream-kasan-gce
2020/05/20 08:22 upstream 03fb3acae4be 67fa1f59 .config console log report ci-upstream-kasan-gce
2020/05/11 15:51 upstream 2ef96a5bb12b f8f57555 .config console log report ci-upstream-kasan-gce-root
2020/06/16 13:56 upstream 7ae77150d94d baca2611 .config console log report ci-upstream-kasan-gce-386
2020/05/22 08:43 upstream d2f8825ab78e 5afa2ddd .config console log report ci-upstream-kasan-gce-386
2020/05/20 21:48 upstream 115a54162a6c 1255f02a .config console log report ci-upstream-kasan-gce-386
2020/05/29 01:14 net-old 2b86cb829976 0d951763 .config console log report ci-upstream-net-this-kasan-gce
2020/05/18 06:32 net-old e3f2d5579c0b 37bccd4e .config console log report ci-upstream-net-this-kasan-gce
2020/05/14 21:19 net-old 9de5d235b60a 2d572622 .config console log report ci-upstream-net-this-kasan-gce
2020/05/12 17:35 net-old 1abfb181e089 160c7698 .config console log report ci-upstream-net-this-kasan-gce
2020/06/26 07:59 net-next-old cb8e59cc8720 aea82c00 .config console log report ci-upstream-net-kasan-gce
2020/06/18 23:32 net-next-old cb8e59cc8720 d45a4d69 .config console log report ci-upstream-net-kasan-gce
2020/06/17 11:33 net-next-old cb8e59cc8720 b9f3810b .config console log report ci-upstream-net-kasan-gce
2020/06/10 10:03 net-next-old cb8e59cc8720 860c4de9 .config console log report ci-upstream-net-kasan-gce
2020/06/04 15:32 net-next-old cb8e59cc8720 b0d1c0d5 .config console log report ci-upstream-net-kasan-gce
2020/06/02 15:00 net-next-old 9a25c1df24a6 52fd7b7d .config console log report ci-upstream-net-kasan-gce
2020/05/31 03:27 net-next-old 4300c7e7fe15 6f3e1c7c .config console log report ci-upstream-net-kasan-gce
2020/05/28 02:45 net-next-old 50ce4c099beb 142a0957 .config console log report ci-upstream-net-kasan-gce
2020/05/25 15:10 net-next-old 06ec313eea4f 30927cd7 .config console log report ci-upstream-net-kasan-gce
2020/05/24 03:34 net-next-old 54b9aca08c9a 96c92ad3 .config console log report ci-upstream-net-kasan-gce
2020/05/23 01:22 net-next-old 199671eadd47 9682898d .config console log report ci-upstream-net-kasan-gce
2020/05/22 08:16 net-next-old 2a330b533462 5afa2ddd .config console log report ci-upstream-net-kasan-gce
2020/05/13 00:16 net-next-old 51fa960d3b51 a44eb8f7 .config console log report ci-upstream-net-kasan-gce
* Struck through repros no longer work on HEAD.