Message-ID: <CACT4Y+bTo34q4=7X8zGL_XVOGoYd7fqhfAbCAWUxsr-N96Kyxw@mail.gmail.com>
Date:   Wed, 2 May 2018 13:23:23 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+bf89c128e05dd6c62523@...kaller.appspotmail.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: general protection fault in lo_ioctl (2)

On Wed, May 2, 2018 at 9:33 AM, syzbot
<syzbot+bf89c128e05dd6c62523@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    fff75eb2a08c Merge tag 'errseq-v4.17' of
> git://git.kernel.o...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?id=5301511529693184
> kernel config:
> https://syzkaller.appspot.com/x/.config?id=6493557782959164711
> dashboard link: https://syzkaller.appspot.com/bug?extid=bf89c128e05dd6c62523
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> userspace arch: i386
> syzkaller
> repro:https://syzkaller.appspot.com/x/repro.syz?id=5000693362458624

#syz dup: INFO: rcu detected stall in blkdev_ioctl

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+bf89c128e05dd6c62523@...kaller.appspotmail.com
>
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 10637 Comm: syz-executor1 Not tainted 4.17.0-rc3+ #52
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:loop_set_fd drivers/block/loop.c:901 [inline]
> RIP: 0010:lo_ioctl+0x1ae8/0x2130 drivers/block/loop.c:1397
> RSP: 0018:ffff8801bd6dfc08 EFLAGS: 00010202
> RAX: 0000000000000037 RBX: ffff8801d296db00 RCX: dffffc0000000000
> RDX: 0000000000000000 RSI: ffffffff84b2cd57 RDI: 00000000000001b8
> RBP: ffff8801bd6dfc80 R08: ffff8801c46943c0 R09: ffffed003b5c46c2
> R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000000 R14: ffff8801b58561a0 R15: ffff8801b58560c0
> FS:  0000000000000000(0000) GS:ffff8801dae00000(0063) knlGS:00000000f7f2eb40
> CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> CR2: 0000000008138024 CR3: 00000001d03df000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  lo_compat_ioctl+0xc1/0x170 drivers/block/loop.c:1602
>  compat_blkdev_ioctl+0x3c2/0x1b20 block/compat_ioctl.c:406
>  __do_compat_sys_ioctl fs/compat_ioctl.c:1461 [inline]
>  __se_compat_sys_ioctl fs/compat_ioctl.c:1407 [inline]
>  __ia32_compat_sys_ioctl+0x221/0x640 fs/compat_ioctl.c:1407
>  do_syscall_32_irqs_on arch/x86/entry/common.c:323 [inline]
>  do_fast_syscall_32+0x345/0xf9b arch/x86/entry/common.c:394
>  entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
> RIP: 0023:0xf7f32cb9
> RSP: 002b:00000000f7f2e0ac EFLAGS: 00000282 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000004c00
> RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> Code: e8 03 80 3c 08 00 0f 85 2c 02 00 00 4d 8b ad f0 00 00 00 48 b9 00 00
> 00 00 00 fc ff df 49 8d bd b8 01 00 00 48 89 f8 48 c1 e8 03 <80> 3c 08 00 0f
> 85 f9 01 00 00 4d 8b ad b8 01 00 00 48 b9 00 00
> RIP: loop_set_fd drivers/block/loop.c:901 [inline] RSP: ffff8801bd6dfc08
> RIP: lo_ioctl+0x1ae8/0x2130 drivers/block/loop.c:1397 RSP: ffff8801bd6dfc08
> ---[ end trace a15583efe355602c ]---
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
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>
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