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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Fri, 25 Oct 2019 13:58:21 +0200
Message-ID: <CACT4Y+Y946C-kyiBSZtyKY7PU4qxrysOfukd42--pXdyTRyjbw@mail.gmail.com>
Subject: Re: KASAN: null-ptr-deref Write in io_wq_cancel_all
To:     syzbot <syzbot+d958a65633ea70280b23@syzkaller.appspotmail.com>
Cc:     linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Al Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@kernel.dk>
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On Fri, Oct 25, 2019 at 1:51 PM syzbot
<syzbot+d958a65633ea70280b23@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    139c2d13 Add linux-next specific files for 20191025
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17ab5a70e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=28fd7a693df38d29
> dashboard link: https://syzkaller.appspot.com/bug?extid=d958a65633ea70280b23
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+d958a65633ea70280b23@syzkaller.appspotmail.com

+Jens

> ==================================================================
> BUG: KASAN: null-ptr-deref in set_bit
> include/asm-generic/bitops-instrumented.h:28 [inline]
> BUG: KASAN: null-ptr-deref in io_wq_cancel_all+0x28/0x2a0 fs/io-wq.c:574
> Write of size 8 at addr 0000000000000004 by task syz-executor.5/17477
>
> CPU: 1 PID: 17477 Comm: syz-executor.5 Not tainted 5.4.0-rc4-next-20191025
> #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x172/0x1f0 lib/dump_stack.c:113
>   __kasan_report.cold+0x5/0x41 mm/kasan/report.c:510
>   kasan_report+0x12/0x20 mm/kasan/common.c:634
>   check_memory_region_inline mm/kasan/generic.c:185 [inline]
>   check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
>   __kasan_check_write+0x14/0x20 mm/kasan/common.c:98
>   set_bit include/asm-generic/bitops-instrumented.h:28 [inline]
>   io_wq_cancel_all+0x28/0x2a0 fs/io-wq.c:574
>   io_ring_ctx_wait_and_kill+0x1e2/0x710 fs/io_uring.c:3679
>   io_uring_release+0x42/0x50 fs/io_uring.c:3691
>   __fput+0x2ff/0x890 fs/file_table.c:280
>   ____fput+0x16/0x20 fs/file_table.c:313
>   task_work_run+0x145/0x1c0 kernel/task_work.c:113
>   exit_task_work include/linux/task_work.h:22 [inline]
>   do_exit+0x904/0x2e60 kernel/exit.c:817
>   do_group_exit+0x135/0x360 kernel/exit.c:921
>   get_signal+0x47c/0x24f0 kernel/signal.c:2734
>   do_signal+0x87/0x1700 arch/x86/kernel/signal.c:815
>   exit_to_usermode_loop+0x286/0x380 arch/x86/entry/common.c:159
>   prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
>   do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x459ef9
> Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f7129716c78 EFLAGS: 00000246 ORIG_RAX: 00000000000001a9
> RAX: 0000000000000005 RBX: 0000000000000002 RCX: 0000000000459ef9
> RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000ebf
> RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f71297176d4
> R13: 00000000004c14ae R14: 00000000004d4c68 R15: 00000000ffffffff
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
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