==================================================================
BUG: KASAN: out-of-bounds in user_mode arch/x86/include/asm/ptrace.h:126 [inline]
BUG: KASAN: out-of-bounds in unwind_next_frame+0x1142/0x17d0 arch/x86/kernel/unwind_orc.c:343
Read of size 8 at addr ffff88821adc7e10 by task syz-executor.4/3551

CPU: 0 PID: 3551 Comm: syz-executor.4 Not tainted 4.14.190-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
 user_mode arch/x86/include/asm/ptrace.h:126 [inline]
 unwind_next_frame+0x1142/0x17d0 arch/x86/kernel/unwind_orc.c:343
 __save_stack_trace+0x90/0x160 arch/x86/kernel/stacktrace.c:44
 save_stack_trace_tsk+0x34/0x40 arch/x86/kernel/stacktrace.c:73
 proc_pid_stack+0x1b2/0x2f0 fs/proc/base.c:459
 proc_single_show+0xe7/0x150 fs/proc/base.c:761
 seq_read+0x4cf/0x1120 fs/seq_file.c:237
 do_loop_readv_writev fs/read_write.c:695 [inline]
 do_loop_readv_writev fs/read_write.c:682 [inline]
 do_iter_read+0x3eb/0x5b0 fs/read_write.c:919
 vfs_readv+0xc8/0x120 fs/read_write.c:981
 do_preadv fs/read_write.c:1065 [inline]
 SYSC_preadv fs/read_write.c:1115 [inline]
 SyS_preadv+0x15a/0x200 fs/read_write.c:1110
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c369
RSP: 002b:00007f46e5892c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00000000000241c0 RCX: 000000000045c369
RDX: 0000000000000375 RSI: 00000000200017c0 RDI: 0000000000000006
RBP: 000000000078c130 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078c0ec
R13: 00007ffc1e15e28f R14: 00007f46e58939c0 R15: 000000000078c0ec

The buggy address belongs to the page:
page:ffffea00086b71c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x57ffe0000000000()
raw: 057ffe0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 0000000100000001 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88821adc7d00: f1 f1 04 f2 04 f2 04 f2 00 00 f2 f2 00 00 f2 f2
 ffff88821adc7d80: 00 00 00 f2 f2 f2 f2 f2 00 00 00 f3 f3 f3 f3 f3
>ffff88821adc7e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1
                            ^
 ffff88821adc7e80: f1 00 f2 f2 f2 00 00 f3 f3 00 00 00 00 00 00 00
 ffff88821adc7f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================