KASAN: out-of-bounds Read in update_stack_state

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 846e8dd47c26 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16ec94a1400000
kernel config: https://syzkaller.appspot.com/x/.config?x=dfb440e26f0a6f6f
dashboard link: https://syzkaller.appspot.com/bug?extid=7afca242bca1a5d29d68
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [b...@alien8.de h...@zytor.com jpoi...@redhat.com
linux-...@vger.kernel.org mi...@redhat.com tg...@linutronix.de
x...@kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7afca2...@syzkaller.appspotmail.com

FAT-fs (loop0): bogus number of reserved sectors
FAT-fs (loop0): Can't find a valid FAT filesystem
FAT-fs (loop0): bogus number of reserved sectors
FAT-fs (loop0): Can't find a valid FAT filesystem
==================================================================
BUG: KASAN: out-of-bounds in update_stack_state+0x5db/0x690
arch/x86/kernel/unwind_frame.c:266
Read of size 8 at addr ffff880180aef0e0 by task syz-executor2/23665

CPU: 0 PID: 23665 Comm: syz-executor2 Not tainted 4.19.0-rc5+ #33
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+0x1c4/0x2b4 lib/dump_stack.c:113
print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
update_stack_state+0x5db/0x690 arch/x86/kernel/unwind_frame.c:266
unwind_next_frame.part.7+0x1ae/0x9e0 arch/x86/kernel/unwind_frame.c:329
unwind_next_frame+0x3e/0x50 arch/x86/kernel/unwind_frame.c:287
__save_stack_trace+0x7d/0xf0 arch/x86/kernel/stacktrace.c:44
save_stack_trace_tsk+0x9c/0xd0 arch/x86/kernel/stacktrace.c:76
proc_pid_stack+0x217/0x3b0 fs/proc/base.c:424
proc_single_show+0x101/0x190 fs/proc/base.c:723
seq_read+0x4af/0x1150 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:700 [inline]
do_iter_read+0x4a3/0x650 fs/read_write.c:924
vfs_readv+0x175/0x1c0 fs/read_write.c:986
do_preadv+0x1cc/0x280 fs/read_write.c:1070
__do_sys_preadv fs/read_write.c:1120 [inline]
__se_sys_preadv fs/read_write.c:1115 [inline]
__x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1115
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457579
Code: 1d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2fc8e58c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000457579
RDX: 1000000000000156 RSI: 0000000020000480 RDI: 0000000000000008
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2fc8e596d4
R13: 00000000004c309c R14: 00000000004d4a40 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea000602bbc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 ffffea000602bbc8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff880180aeef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff880180aef000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff880180aef080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff880180aef100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff880180aef180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.