KASAN: out-of-bounds Read in unwind_next_frame

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c63ee293 Linux 4.19.85
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17330bbae00000
kernel config: https://syzkaller.appspot.com/x/.config?x=cbfad1c8058581ad
dashboard link: https://syzkaller.appspot.com/bug?extid=223ef4134196e1cec19c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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+223ef4...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: out-of-bounds in unwind_next_frame.part.0+0x872/0xa20
arch/x86/kernel/unwind_frame.c:327
Read of size 8 at addr ffff88808a64faa8 by task syz-executor.0/18514

CPU: 1 PID: 18514 Comm: syz-executor.0 Not tainted 4.19.85-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+0x197/0x210 lib/dump_stack.c:118
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report mm/kasan/report.c:412 [inline]
kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:396
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
unwind_next_frame.part.0+0x872/0xa20 arch/x86/kernel/unwind_frame.c:327
unwind_next_frame+0x3b/0x50 arch/x86/kernel/unwind_frame.c:287
__save_stack_trace+0x83/0x100 arch/x86/kernel/stacktrace.c:44
save_stack_trace_tsk arch/x86/kernel/stacktrace.c:76 [inline]
save_stack_trace_tsk+0x9e/0xd0 arch/x86/kernel/stacktrace.c:69
proc_pid_stack+0x1c4/0x2c0 fs/proc/base.c:456
proc_single_show+0xf0/0x180 fs/proc/base.c:755
seq_read+0x4ca/0x1110 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:701 [inline]
do_loop_readv_writev fs/read_write.c:688 [inline]
do_iter_read+0x490/0x640 fs/read_write.c:925
vfs_readv+0xf0/0x160 fs/read_write.c:987
do_preadv+0x1c4/0x280 fs/read_write.c:1071
__do_sys_preadv fs/read_write.c:1121 [inline]
__se_sys_preadv fs/read_write.c:1116 [inline]
__x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1116
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a639
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f797b9d1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045a639
RDX: 10000000000002a1 RSI: 0000000020000480 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f797b9d26d4
R13: 00000000004c7eb1 R14: 00000000004dddd0 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea00022993c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 0000000000000000 ffffffff02290101 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808a64f980: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00
ffff88808a64fa00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
> ffff88808a64fa80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff88808a64fb00: 00 00 00 00 f1 f1 f1 f1 00 f3 f3 f3 00 00 00 00
ffff88808a64fb80: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
==================================================================


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[syzbot]

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