Date:   Mon, 30 Oct 2017 22:53:21 +0300
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot 
        <bot+2af19c9e1ffe4d4ee1d16c56ae7580feaee75765@...kaller.appspotmail.com>
Cc:     dvhart@...radead.org, LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        syzkaller-bugs@...glegroups.com,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: WARNING in get_pi_state

On Mon, Oct 30, 2017 at 10:44 PM, syzbot
<bot+2af19c9e1ffe4d4ee1d16c56ae7580feaee75765@...kaller.appspotmail.com>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> 8fd0520d9cec0896d48d3921bc642a9ee81eae0c
> git://git.cmpxchg.org/linux-mmots.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers


Also happened on more recent commits, including upstream
0787643a5f6aad1f0cdeb305f7fe492b71943ea4:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 6170 at kernel/futex.c:818
get_pi_state+0x15b/0x190 kernel/futex.c:818
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 6170 Comm: syz-executor1 Not tainted 4.14.0-rc5+ #142
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 panic+0x1e4/0x417 kernel/panic.c:181
 __warn+0x1c4/0x1d9 kernel/panic.c:542
 report_bug+0x211/0x2d0 lib/bug.c:183
 fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178
 do_trap_no_signal arch/x86/kernel/traps.c:212 [inline]
 do_trap+0x260/0x390 arch/x86/kernel/traps.c:261
 do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311
 invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
RIP: 0010:get_pi_state+0x15b/0x190 kernel/futex.c:818
RSP: 0018:ffff8801cddbf1a0 EFLAGS: 00010097
RAX: ffff8801c9d662c0 RBX: 0000000000000000 RCX: 1ffff10039bb7e39
RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff8801d04f4d40
RBP: ffff8801cddbf230 R08: 0000000000000001 R09: 1ffff10039bb7e26
R10: ffff8801cddbf0f8 R11: 0000000000000002 R12: 1ffff10039bb7e35
R13: ffff8801d04f4d40 R14: 1ffff10039bb7e39 R15: ffff8801d04f4df0
 exit_pi_state_list+0x556/0x7a0 kernel/futex.c:932
 mm_release+0x46d/0x590 kernel/fork.c:1148
 exit_mm kernel/exit.c:499 [inline]
 do_exit+0x481/0x1ad0 kernel/exit.c:852
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73f/0x16d0 kernel/signal.c:2334
 do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:808
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath+0x42f/0x510 arch/x86/entry/common.c:266
 entry_SYSCALL_64_fastpath+0xbc/0xbe
RIP: 0033:0x452719
RSP: 002b:00007effb0461be8 EFLAGS: 00000212 ORIG_RAX: 00000000000000ca
RAX: 0000000000000000 RBX: 0000000000758190 RCX: 0000000000452719
RDX: 0000000000000004 RSI: 000080000000000b RDI: 000000002000cffc
RBP: 000000000000008f R08: 0000000020048000 R09: 0000000000000000
R10: 0000000020edfff0 R11: 0000000000000212 R12: 00000000006eee08
R13: 00000000ffffffff R14: 00007effb04626d4 R15: 0000000000000004



> WARNING: CPU: 1 PID: 24353 at kernel/futex.c:818 get_pi_state+0x15b/0x190
> kernel/futex.c:818
> Kernel panic - not syncing: panic_on_warn set ...
>
> CPU: 1 PID: 24353 Comm: syzkaller121915 Not tainted 4.14.0-rc2-mm1+ #10
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:16 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:52
>  panic+0x1e4/0x417 kernel/panic.c:181
>  __warn+0x1c4/0x1d9 kernel/panic.c:542
>  report_bug+0x211/0x2d0 lib/bug.c:183
>  fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178
>  do_trap_no_signal arch/x86/kernel/traps.c:212 [inline]
>  do_trap+0x260/0x390 arch/x86/kernel/traps.c:261
>  do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298
>  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311
>  invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
> RIP: 0010:get_pi_state+0x15b/0x190 kernel/futex.c:818
> RSP: 0018:ffff8801bf2a77a8 EFLAGS: 00010097
> RAX: ffff8801cb2d05c0 RBX: 0000000000000000 RCX: 1ffff10037e54efa
> RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff8801d892cd40
> RBP: ffff8801bf2a7838 R08: ffff8801cb2d1880 R09: 1ffff10037e54edf
> R10: ffff8801cb2d05c0 R11: 0000000000000002 R12: 1ffff10037e54ef6
> R13: ffff8801d892cd40 R14: 1ffff10037e54efa R15: ffff8801d892ce00
>  exit_pi_state_list+0x556/0x7a0 kernel/futex.c:932
>  mm_release+0x46d/0x590 kernel/fork.c:1191
>  exit_mm kernel/exit.c:499 [inline]
>  do_exit+0x481/0x1b00 kernel/exit.c:852
>  SYSC_exit kernel/exit.c:937 [inline]
>  SyS_exit+0x22/0x30 kernel/exit.c:935
>  entry_SYSCALL_64_fastpath+0x1f/0xbe
> RIP: 0033:0x40337e
> RSP: 002b:00007fdd99af2d20 EFLAGS: 00000246 ORIG_RAX: 000000000000003c
> RAX: ffffffffffffffda RBX: 00007fdd99af3700 RCX: 000000000040337e
> RDX: 000000000000003c RSI: 00000000007fb000 RDI: 0000000000000000
> RBP: 0000000000000086 R08: 0000000020048000 R09: 0000000000000000
> R10: 000000002000b000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffcfc38d0bf R14: 00007fdd99af39c0 R15: 0000000000000000
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
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