Date:   Wed, 21 Feb 2018 12:59:02 -0800
From:   syzbot <syzbot+2990ca6e76c080858a9c@...kaller.appspotmail.com>
To:     hpa@...or.com, jpoimboe@...hat.com, linux-kernel@...r.kernel.org,
        mbenes@...e.cz, mhiramat@...nel.org, mingo@...hat.com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de, x86@...nel.org
Subject: KASAN: stack-out-of-bounds Read in update_stack_state

Hello,

syzbot hit the following crash on bpf-next commit
0b6b8a3dd86db78c3f38587d667d77065c75e4f8 (Thu Feb 15 09:22:55 2018 +0000)
Merge branch 'bpf-misc-selftest-improvements'

So far this crash happened 21 times on bpf-next.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2990ca6e76c080858a9c@...kaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

audit: type=1400 audit(1519168770.631:6): avc:  denied  { map } for   
pid=4150 comm="bash" path="/bin/bash" dev="sda1" ino=1457  
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
audit: type=1400 audit(1519168776.932:7): avc:  denied  { map } for   
pid=4164 comm="syzkaller659137" path="/root/syzkaller659137685" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: stack-out-of-bounds in __read_once_size  
include/linux/compiler.h:183 [inline]
BUG: KASAN: stack-out-of-bounds in update_stack_state+0x6ea/0x700  
arch/x86/kernel/unwind_frame.c:270
Read of size 8 at addr ffff8801a9e57198 by task syzkaller659137/4164

CPU: 0 PID: 4164 Comm: syzkaller659137 Not tainted 4.16.0-rc1+ #14
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+0x194/0x257 lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report+0x23b/0x360 mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  __read_once_size include/linux/compiler.h:183 [inline]
  update_stack_state+0x6ea/0x700 arch/x86/kernel/unwind_frame.c:270
  __unwind_start+0xfd/0x330 arch/x86/kernel/unwind_frame.c:404
  unwind_start arch/x86/include/asm/unwind.h:54 [inline]
  perf_callchain_kernel+0x2fb/0x610 arch/x86/events/core.c:2350
  get_perf_callchain+0x48f/0xa50 kernel/events/callchain.c:205
  perf_callchain kernel/events/core.c:6003 [inline]
  perf_prepare_sample+0x118b/0x16f0 kernel/events/core.c:6029
  __perf_event_output kernel/events/core.c:6143 [inline]
  perf_event_output_forward+0xef/0x260 kernel/events/core.c:6161
  __perf_event_overflow+0x207/0x490 kernel/events/core.c:7397
  perf_swevent_overflow+0x20c/0x2c0 kernel/events/core.c:7473
  perf_swevent_event+0x10e/0x270 kernel/events/core.c:7506
  do_perf_sw_event kernel/events/core.c:7614 [inline]
  ___perf_sw_event+0x491/0x6d0 kernel/events/core.c:7645
  perf_sw_event_sched include/linux/perf_event.h:1044 [inline]
  perf_event_task_sched_out include/linux/perf_event.h:1082 [inline]
  prepare_task_switch kernel/sched/core.c:2638 [inline]
  context_switch kernel/sched/core.c:2815 [inline]
  __schedule+0xd53/0x2040 kernel/sched/core.c:3435
  schedule+0xf5/0x430 kernel/sched/core.c:3494
  exit_to_usermode_loop+0x1d1/0x2f0 arch/x86/entry/common.c:152
  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
  do_syscall_64+0x6ed/0x940 arch/x86/entry/common.c:292
  entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x43fe99
RSP: 002b:00007ffed9993ee8 EFLAGS: 00000203 ORIG_RAX: 0000000000000001
RAX: 0000000000000012 RBX: 00000000ffffffff RCX: 000000000043fe99
RDX: 0000000000000012 RSI: 00000000004a1184 RDI: 0000000000000001
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000203 R12: 00000000004017c0
R13: 0000000000401850 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0006a795c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 ffffea0006a70101 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801a9e57080: 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00 00 00 00
  ffff8801a9e57100: f2 f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00
> ffff8801a9e57180: 00 00 f1 f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 f8 f2
                             ^
  ffff8801a9e57200: f2 f2 f2 f2 f2 f2 00 00 00 f2 f3 f3 f3 f3 00 00
  ffff8801a9e57280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1
==================================================================


---
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