KASAN: slab-out-of-bounds Write in __unwind_start (2)

[syzbot]

Hello,

syzkaller hit the following crash on
e56d565d67ae7dd6b25ce6a331c43e691ff1d247
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

Unfortunately, I don't have any reproducer for this bug yet.
CC: [h...@zytor.com jpoi...@redhat.com linux-...@vger.kernel.org
mi...@redhat.com tg...@linutronix.de x...@kernel.org]

attempt to access beyond end of device
unknown-block(7,0): rw=0, want=0, limit=256
attempt to access beyond end of device
unknown-block(7,0): rw=0, want=0, limit=256
==================================================================
BUG: KASAN: slab-out-of-bounds in memset include/linux/string.h:326 [inline]
BUG: KASAN: slab-out-of-bounds in __unwind_start+0x2d/0x330
arch/x86/kernel/unwind_frame.c:389
Write of size 88 at addr ffff8801d250fe98 by task loop0/3865

CPU: 1 PID: 3865 Comm: loop0 Not tainted 4.15.0-rc2+ #210
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:

Allocated by task 2169817619:
(stack is not available)

Freed by task 2278480280:
(stack is not available)

The buggy address belongs to the object at ffff8801d250e800
which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 1688 bytes to the right of
4096-byte region [ffff8801d250e800, ffff8801d250f800)
The buggy address belongs to the page:
page:00000000c9ed0821 count:1 mapcount:0 mapping:00000000514eb3e6 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d250e800 0000000000000000 0000000100000001
raw: ffffea000762e420 ffffea0007466820 ffff8801db000dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d250fd80: fc fc fc fc 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801d250fe00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
> ffff8801d250fe80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
^
ffff8801d250ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801d250ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3865 Comm: loop0 Tainted: G B 4.15.0-rc2+ #210
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Dmitry Vyukov]

does not look actionable/legit

#syz invalid

On Mon, Dec 11, 2017 at 4:26 AM, syzbot
<bot+5ad464715445efda92...@syzkaller.appspotmail.com>
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