KASAN: use-after-free Read in tick_sched_handle (2)

[syzbot]

Hello,

syzbot hit the following crash on net-next commit
6bb46bc57c8e9ce947cc605e555b7204b44d2b10 (Fri Jan 26 16:00:23 2018 +0000)
Merge branch 'cxgb4-fix-dump-collection-when-firmware-crashed'

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.
CC: [fwei...@gmail.com linux-...@vger.kernel.org mi...@kernel.org
tg...@linutronix.de]

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+79129b...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for
details.
If you forward the report, please keep this part and the footer.

==================================================================
BUG: KASAN: use-after-free in tick_sched_handle+0x149/0x160
kernel/time/tick-sched.c:153
Read of size 8 at addr ffff8801cae2fc60 by task syz-executor2/26843

CPU: 1 PID: 26843 Comm: syz-executor2 Not tainted 4.15.0-rc9+ #212
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
tick_sched_handle+0x149/0x160 kernel/time/tick-sched.c:153
tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
__run_hrtimer kernel/time/hrtimer.c:1211 [inline]
__hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1275
hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1309
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:937
</IRQ>

Allocated by task 642:
(stack is not available)

Freed by task 21:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3488 [inline]
kfree+0xd6/0x260 mm/slab.c:3803
call_usermodehelper_freeinfo kernel/umh.c:43 [inline]
umh_complete+0x5c/0x90 kernel/umh.c:57
call_usermodehelper_exec_sync kernel/umh.c:152 [inline]
call_usermodehelper_exec_work+0x15a/0x2c0 kernel/umh.c:175
process_one_work+0xbbf/0x1b10 kernel/workqueue.c:2113
worker_thread+0x223/0x1990 kernel/workqueue.c:2247
kthread+0x33c/0x400 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:541

The buggy address belongs to the object at ffff8801cae2fc00
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 96 bytes inside of
128-byte region [ffff8801cae2fc00, ffff8801cae2fc80)
The buggy address belongs to the page:
page:ffffea00072b8bc0 count:1 mapcount:0 mapping:ffff8801cae2f000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cae2f000 0000000000000000 0000000100000015
raw: ffffea0006b168a0 ffffea0007638ba0 ffff8801dac00640 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801cae2fb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801cae2fb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801cae2fc00: 00 00 00 00 00 00 00 00 00 00 fb fb fb fb fb fb
^
ffff8801cae2fc80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff8801cae2fd00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzk...@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug
report.
Note: all commands must start from beginning of the line in the email body.
To upstream this report, please reply with:
#syz upstream

[Dmitry Vyukov]

old bug bankruptcy

#syz invalid

> --
> You received this message because you are subscribed to the Google Groups
> "syzkaller-upstream-moderation" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to syzkaller-upstream-m...@googlegroups.com.
> To post to this group, send email to
> syzkaller-upst...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/syzkaller-upstream-moderation/001a113f634450c0020563c76e87%40google.com.
> For more options, visit https://groups.google.com/d/optout.

[George K]

In marking " #syz invalid" what does " old bug bankruptcy" mean?

I don't see this phrase described anywhere and am wondering the real reason a crash is marked "invalid".

Thank you,

George

[Dmitry Vyukov]

On Thu, 22 Jul 2021 at 14:03, George K <gk56...@gmail.com> wrote:
>
> In marking " #syz invalid" what does " old bug bankruptcy" mean?
>
> I don't see this phrase described anywhere and am wondering the real reason a crash is marked "invalid".

Hi George,

I guess I was invalidating all old bugs that did not look sane (e.g.
an induced bug due to a previous memory corruption) and/or happened a
few times and then stopped happening. Basically a bankruptcy for a
backlog of older bugs. The idea is that it's better to have a smaller
number of more actionable bugs than a huge pile of garbage.

> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-upstream-moderation/17aaf1ef-3029-443b-8146-83d6235a170cn%40googlegroups.com.