lkml.org 
[lkml]   [2021]   [Nov]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    Subject[syzbot] possible deadlock in __io_commit_cqring_flush
    From
    Hello,

    syzbot found the following issue on:

    HEAD commit: a4849f6000e2 Merge tag 'drm-fixes-2021-11-26' of git://ano..
    git tree: upstream
    console output: https://syzkaller.appspot.com/x/log.txt?x=10d5f726b00000
    kernel config: https://syzkaller.appspot.com/x/.config?x=75f05fb8d1a152d3
    dashboard link: https://syzkaller.appspot.com/bug?extid=ff49a3059d49b0ca0eec
    compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

    Unfortunately, I don't have any reproducer for this issue yet.

    IMPORTANT: if you fix the issue, please add the following tag to the commit:
    Reported-by: syzbot+ff49a3059d49b0ca0eec@syzkaller.appspotmail.com

    ============================================
    WARNING: possible recursive locking detected
    5.16.0-rc2-syzkaller #0 Not tainted
    --------------------------------------------
    syz-executor.1/8766 is trying to acquire lock:
    ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
    ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_flush_timeouts fs/io_uring.c:1587 [inline]
    ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: __io_commit_cqring_flush+0x108/0x50d fs/io_uring.c:1618

    but task is already holding lock:
    ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
    ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_poll_remove_all+0x50/0x235 fs/io_uring.c:5702

    other info that might help us debug this:
    Possible unsafe locking scenario:

    CPU0
    ----
    lock(&ctx->timeout_lock);
    lock(&ctx->timeout_lock);

    *** DEADLOCK ***

    May be due to missing lock nesting notation

    2 locks held by syz-executor.1/8766:
    #0: ffff888096b573d8 (&ctx->completion_lock#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:349 [inline]
    #0: ffff888096b573d8 (&ctx->completion_lock#2){+.+.}-{2:2}, at: io_poll_remove_all+0x48/0x235 fs/io_uring.c:5701
    #1: ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:374 [inline]
    #1: ffff888096b57418 (&ctx->timeout_lock){+.+.}-{2:2}, at: io_poll_remove_all+0x50/0x235 fs/io_uring.c:5702

    stack backtrace:
    CPU: 0 PID: 8766 Comm: syz-executor.1 Not tainted 5.16.0-rc2-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Call Trace:
    <TASK>
    __dump_stack lib/dump_stack.c:88 [inline]
    dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
    print_deadlock_bug kernel/locking/lockdep.c:2956 [inline]
    check_deadlock kernel/locking/lockdep.c:2999 [inline]
    validate_chain kernel/locking/lockdep.c:3788 [inline]
    __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027
    lock_acquire kernel/locking/lockdep.c:5637 [inline]
    lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
    __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
    _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170
    spin_lock_irq include/linux/spinlock.h:374 [inline]
    io_flush_timeouts fs/io_uring.c:1587 [inline]
    __io_commit_cqring_flush+0x108/0x50d fs/io_uring.c:1618
    io_commit_cqring fs/io_uring.c:1626 [inline]
    io_poll_remove_one fs/io_uring.c:5684 [inline]
    io_poll_remove_one.cold+0xd/0x12 fs/io_uring.c:5674
    io_poll_remove_all+0x1af/0x235 fs/io_uring.c:5709
    io_ring_ctx_wait_and_kill+0x1cc/0x322 fs/io_uring.c:9534
    io_uring_release+0x42/0x46 fs/io_uring.c:9554
    __fput+0x286/0x9f0 fs/file_table.c:280
    task_work_run+0xdd/0x1a0 kernel/task_work.c:164
    tracehook_notify_resume include/linux/tracehook.h:189 [inline]
    exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
    exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207
    __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
    syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
    do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
    entry_SYSCALL_64_after_hwframe+0x44/0xae
    RIP: 0033:0x7f087b422ae9
    Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
    RSP: 002b:00007f0878977188 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
    RAX: 0000000020ffa000 RBX: 00007f087b536020 RCX: 00007f087b422ae9
    RDX: 0000000003000001 RSI: 0000000000004000 RDI: 0000000020ffa000
    RBP: 00007f087b47cf6d R08: 0000000000000003 R09: 0000000010000000
    R10: 0000000000000012 R11: 0000000000000246 R12: 0000000000000000
    R13: 00007ffe7626bd9f R14: 00007f0878977300 R15: 0000000000022000
    </TASK>


    ---
    This report 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 issue. See:
    https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

    \
     
     \ /
      Last update: 2021-11-26 13:43    [W:3.951 / U:0.016 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site