syzbot


KASAN: use-after-free Read in bpf_csum_update

Status: fixed on 2018/07/09 18:05
Subsystems: bpf net
[Documentation on labels]
Reported-by: syzbot+3d0b2441dbb71751615e@syzkaller.appspotmail.com
Fix commit: 58990d1ff3f7 bpf: reject passing modified ctx to helper functions
First crash: 2190d, last: 2190d
Discussions (4)
Title Replies (including bot) Last reply
[PATCH 4.14 00/62] 4.14.164-stable review 66 (66) 2020/01/13 15:47
[PATCH 4.17 00/67] 4.17.7-stable review 74 (74) 2018/07/17 09:41
KASAN: use-after-free Read in bpf_csum_update 1 (2) 2018/06/08 09:52
[PATCH bpf] bpf: reject passing modified ctx to helper functions 4 (4) 2018/06/07 19:43

Sample crash report:
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KASAN: use-after-free in ____bpf_csum_update net/core/filter.c:1907 [inline]
BUG: KASAN: use-after-free in bpf_csum_update+0xb4/0xc0 net/core/filter.c:1901
Read of size 1 at addr ffff8801ad062f10 by task syz-executor354/4488

CPU: 1 PID: 4488 Comm: syz-executor354 Not tainted 4.17.0-rc6+ #29
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+0x1b9/0x294 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 ____bpf_csum_update net/core/filter.c:1907 [inline]
 bpf_csum_update+0xb4/0xc0 net/core/filter.c:1901

The buggy address belongs to the page:
page:ffffea0006b41880 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: ffffea0006b41820 ffffea0006b671a0 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ad062e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801ad062e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8801ad062f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                         ^
 ffff8801ad062f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8801ad063000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/06/01 19:28 bpf-next bcece5dc40b9 2f93b54f .config console log report syz C ci-upstream-bpf-next-kasan-gce
* Struck through repros no longer work on HEAD.