KASAN: slab-out-of-bounds Read in vsscanf (2)

Status: fixed on 2020/09/16 22:51
Subsystems: lsm
[Documentation on labels]
Reported-by: syzbot+a22c6092d003d6fe1122@syzkaller.appspotmail.com
Fix commit: a6bd4f6d9b07 Smack: fix another vsscanf out of bounds
First crash: 2201d, last: 2184d
Cause bisection: failed (error log, bisect log)
  
▶ ▼ Discussions (10)
Title Replies (including bot) Last reply
[PATCH 4.4 000/149] 4.4.233-rc1 review 163 (163) 2020/10/31 20:04
[PATCH 4.9 000/212] 4.9.233-rc1 review 220 (220) 2020/08/21 09:40
[PATCH 4.19 000/168] 4.19.140-rc1 review 183 (183) 2020/08/21 08:05
[PATCH 4.14 000/228] 4.14.194-rc1 review 234 (234) 2020/08/21 06:59
[PATCH 5.8 000/464] 5.8.2-rc1 review 475 (475) 2020/08/19 06:11
[PATCH 5.4 000/270] 5.4.59-rc1 review 275 (275) 2020/08/18 22:37
[PATCH 5.7 000/393] 5.7.16-rc1 review 398 (398) 2020/08/18 22:36
[PATCH] smack: fix slab-out-of-bounds by checking for overflow 2 (2) 2020/07/27 17:38
[PATCH 1/2] Smack: fix another vsscanf out of bounds 2 (2) 2020/07/23 16:38
KASAN: slab-out-of-bounds Read in vsscanf (2) 0 (1) 2020/07/22 18:32
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-out-of-bounds Read in vsscanf lsm 17 syz, C done 61 2213d 2315d 15/29 fixed on 2020/07/17 17:58
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2020/07/25 11:31 16m bkkarthik@pesu.pes.edu patch https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master OK

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3321
Read of size 1 at addr ffff888097d682b8 by task syz-executor980/6804

CPU: 0 PID: 6804 Comm: syz-executor980 Not tainted 5.8.0-rc5-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+0x1f0/0x31e lib/dump_stack.c:118
 print_address_description+0x66/0x5a0 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 vsscanf+0x2666/0x2ef0 lib/vsprintf.c:3321
 sscanf+0x6c/0x90 lib/vsprintf.c:3527
 smk_set_cipso+0x374/0x6c0 security/smack/smackfs.c:908
 vfs_write+0x2dd/0xc70 fs/read_write.c:576
 ksys_write+0x11b/0x220 fs/read_write.c:631
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4402d9
Code: Bad RIP value.
RSP: 002b:00007ffe89010db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402d9
RDX: 0000000000000037 RSI: 0000000020000040 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000014 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401ae0
R13: 0000000000401b70 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6804:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494
 __do_kmalloc mm/slab.c:3656 [inline]
 __kmalloc_track_caller+0x249/0x320 mm/slab.c:3671
 memdup_user_nul+0x26/0xf0 mm/util.c:259
 smk_set_cipso+0xff/0x6c0 security/smack/smackfs.c:859
 vfs_write+0x2dd/0xc70 fs/read_write.c:576
 ksys_write+0x11b/0x220 fs/read_write.c:631
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 4906:
 save_stack mm/kasan/common.c:48 [inline]
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 tomoyo_path_number_perm+0x525/0x690 security/tomoyo/file.c:736
 tomoyo_path_mknod+0x128/0x150 security/tomoyo/tomoyo.c:240
 security_path_mknod+0xdc/0x160 security/security.c:1077
 may_o_create fs/namei.c:2919 [inline]
 lookup_open fs/namei.c:3060 [inline]
 open_last_lookups fs/namei.c:3169 [inline]
 path_openat+0xbe8/0x37f0 fs/namei.c:3357
 do_filp_open+0x191/0x3a0 fs/namei.c:3387
 do_sys_openat2+0x463/0x770 fs/open.c:1179
 do_sys_open fs/open.c:1195 [inline]
 ksys_open include/linux/syscalls.h:1388 [inline]
 __do_sys_open fs/open.c:1201 [inline]
 __se_sys_open fs/open.c:1199 [inline]
 __x64_sys_open+0x1af/0x1e0 fs/open.c:1199
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888097d68280
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 56 bytes inside of
 64-byte region [ffff888097d68280, ffff888097d682c0)
The buggy address belongs to the page:
page:ffffea00025f5a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888097d68c80
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000288fe08 ffffea00026f38c8 ffff8880aa400380
raw: ffff888097d68c80 ffff888097d68000 000000010000001e 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888097d68180: 00 00 00 00 01 fc fc fc fc fc fc fc fc fc fc fc
 ffff888097d68200: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888097d68280: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc
                                        ^
 ffff888097d68300: 00 00 00 00 01 fc fc fc fc fc fc fc fc fc fc fc
 ffff888097d68380: 00 00 00 00 01 fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/07/19 20:54 upstream f932d58abc38 9c812472 .config console log report syz C ci-upstream-kasan-gce-smack-root
2020/08/05 05:54 upstream c0842fbc1b18 80a06902 .config console log report ci-upstream-kasan-gce-smack-root
2020/07/31 21:49 upstream d8b9faec54ae d895b3be .config console log report ci-upstream-kasan-gce-smack-root
2020/07/31 13:03 upstream 83bdc7275e62 8df85ed9 .config console log report ci-upstream-kasan-gce-smack-root
2020/07/19 20:44 upstream f932d58abc38 9c812472 .config console log report ci-upstream-kasan-gce-smack-root
* Struck through repros no longer work on HEAD.