KASAN: out-of-bounds Read in unwind_get_return_address

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 8c01d009 UPSTREAM: arm64: restore get_current() optimisation
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=179ca2e7800000
kernel config: https://syzkaller.appspot.com/x/.config?x=a54f56879744de40
dashboard link: https://syzkaller.appspot.com/bug?extid=e1743df3e775ccaefe11
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13851447800000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16b7e4e7800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e1743d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: out-of-bounds in unwind_get_return_address+0x98/0xb0
arch/x86/kernel/unwind_frame.c:17
Read of size 8 at addr ffff8801d8ccf8e0 by task syz-executor806/3800

CPU: 1 PID: 3800 Comm: syz-executor806 Not tainted 4.9.96-g8c01d00 #11
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
ffff8801d8d677c8 ffffffff81eb0b69 ffffea00076333c0 ffff8801d8ccf8e0
0000000000000000 ffff8801d8ccf8e8 ffff8801d96d48c0 ffff8801d8d67800
ffffffff8156540b ffff8801d8ccf8e0 0000000000000008 0000000000000000
Call Trace:
[<ffffffff81eb0b69>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81eb0b69>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff8156540b>] print_address_description+0x6c/0x234
mm/kasan/report.c:256
[<ffffffff81565815>] kasan_report_error mm/kasan/report.c:355 [inline]
[<ffffffff81565815>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
[<ffffffff81539494>] __asan_report_load8_noabort+0x14/0x20
mm/kasan/report.c:433
[<ffffffff810d0c08>] unwind_get_return_address+0x98/0xb0
arch/x86/kernel/unwind_frame.c:17
[<ffffffff8107addd>] __save_stack_trace+0x8d/0xf0
arch/x86/kernel/stacktrace.c:43
[<ffffffff8107aea8>] save_stack_trace_tsk+0x48/0x70
arch/x86/kernel/stacktrace.c:71
[<ffffffff816d5378>] proc_pid_stack+0x148/0x220 fs/proc/base.c:467
[<ffffffff816d681d>] proc_single_show+0xfd/0x170 fs/proc/base.c:769
[<ffffffff815eaa16>] seq_read+0x4b6/0x12e0 fs/seq_file.c:240
[<ffffffff8156cc95>] do_loop_readv_writev.part.18+0xd5/0x280
fs/read_write.c:718
[<ffffffff81570be5>] do_loop_readv_writev fs/read_write.c:707 [inline]
[<ffffffff81570be5>] do_readv_writev+0x565/0x7a0 fs/read_write.c:873
[<ffffffff81570ea4>] vfs_readv+0x84/0xc0 fs/read_write.c:897
[<ffffffff81570fc6>] do_readv+0xe6/0x260 fs/read_write.c:923
[<ffffffff81574827>] SYSC_readv fs/read_write.c:1010 [inline]
[<ffffffff81574827>] SyS_readv+0x27/0x30 fs/read_write.c:1007
[<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
[<ffffffff839f3313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

The buggy address belongs to the page:
page:ffffea00076333c0 count:0 mapcount:0 mapping: (null) index:0x0
flags: 0x8000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d8ccf780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801d8ccf800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801d8ccf880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff8801d8ccf900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801d8ccf980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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