KASAN: out-of-bounds Read in update_stack_state

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 0dba8e72 ANDROID: dm: prevent default-key from being enabl..
git tree: android-5.4
console output: https://syzkaller.appspot.com/x/log.txt?x=12facfa5e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e0c0ec90b0eccbb
dashboard link: https://syzkaller.appspot.com/bug?extid=3e297fdcbcc15c223b3e
compiler: Android (6032204 based on r370808) clang version 10.0.1 (https://android.googlesource.com/toolchain/llvm-project 6e765c10313d15c02ab29977a82938f66742c3a9)

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+3e297f...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: out-of-bounds in user_mode arch/x86/include/asm/ptrace.h:131 [inline]
BUG: KASAN: out-of-bounds in update_stack_state+0x376/0x5b0 arch/x86/kernel/unwind_frame.c:244
Read of size 8 at addr ffff8881c778fcf0 by task syz-executor.3/21800

CPU: 1 PID: 21800 Comm: syz-executor.3 Tainted: G W 5.4.18-syzkaller-00147-g0dba8e724663 #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+0x1b0/0x228 lib/dump_stack.c:118
print_address_description+0x96/0x5d0 mm/kasan/report.c:374
__kasan_report+0x14b/0x1c0 mm/kasan/report.c:506
kasan_report+0x26/0x50 mm/kasan/common.c:634
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
user_mode arch/x86/include/asm/ptrace.h:131 [inline]
update_stack_state+0x376/0x5b0 arch/x86/kernel/unwind_frame.c:244
unwind_next_frame+0x415/0x870 arch/x86/kernel/unwind_frame.c:311
arch_stack_walk+0xb4/0xe0 arch/x86/kernel/stacktrace.c:25
stack_trace_save_tsk+0x2d5/0x470 kernel/stacktrace.c:151
proc_pid_stack+0x137/0x200 fs/proc/base.c:455
proc_single_show+0xd5/0x130 fs/proc/base.c:757
seq_read+0x4a8/0xdd0 fs/seq_file.c:229
do_loop_readv_writev fs/read_write.c:717 [inline]
do_iter_read+0x4a2/0x5b0 fs/read_write.c:938
vfs_readv fs/read_write.c:1000 [inline]
do_preadv+0x1f4/0x330 fs/read_write.c:1092
__do_sys_preadv fs/read_write.c:1142 [inline]
__se_sys_preadv fs/read_write.c:1137 [inline]
__x64_sys_preadv+0x9e/0xb0 fs/read_write.c:1137
do_syscall_64+0xc0/0x100 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45b3b9
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:00007f7843ef8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007f7843ef96d4 RCX: 000000000045b3b9
RDX: 000000000000022a RSI: 00000000200017c0 RDI: 0000000000000008
RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000851 R14: 00000000004c9c95 R15: 000000000075c124

The buggy address belongs to the page:
page:ffffea00071de3c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
raw: 8000000000000000 0000000000000000 ffffffff071d0101 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881c778fb80: 00 00 00 00 f2 f2 f2 f2 00 00 00 00 f2 f2 f2 f2
ffff8881c778fc00: 00 00 00 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 00
>ffff8881c778fc80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff8881c778fd00: f1 f1 f1 f1 00 00 f3 f3 00 00 00 00 00 00 00 00
ffff8881c778fd80: 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.