Message-ID: <CACT4Y+abV9E6wAwxeTD+DUG0-VknM-CPMZW_p3SXstiqwRH=tQ@mail.gmail.com>
Date:   Mon, 14 Nov 2022 10:48:41 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+8040d16d30c215f821de@...kaller.appspotmail.com>
Cc:     bongsu.jeon@...sung.com, krzysztof.kozlowski@...aro.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] possible deadlock in virtual_nci_close

On Mon, 14 Nov 2022 at 04:11, syzbot
<syzbot+8040d16d30c215f821de@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    af7a05689189 Merge tag 'mips-fixes_6.1_1' of git://git.ker..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13d30249880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9d1d2dd6d424a076
> dashboard link: https://syzkaller.appspot.com/bug?extid=8040d16d30c215f821de
> compiler:       aarch64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: arm64
>
> 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+8040d16d30c215f821de@...kaller.appspotmail.com

This should be fixed by the following commit when/if it's merged. The
commit removes nci_mutex.

nfc: Allow to create multiple virtual nci devices
https://lore.kernel.org/all/20221104170422.979558-1-dvyukov@google.com/


> nci: __nci_request: wait_for_completion_interruptible_timeout failed 0
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.1.0-rc4-syzkaller-00372-gaf7a05689189 #0 Not tainted
> ------------------------------------------------------
> syz-executor.1/8551 is trying to acquire lock:
> ffff80000e6854c8 (nci_mutex){+.+.}-{3:3}, at: virtual_nci_close+0x2c/0x60 drivers/nfc/virtual_ncidev.c:44
>
> but task is already holding lock:
> ffff000030115350 (&ndev->req_lock){+.+.}-{3:3}, at: nci_close_device+0x5c/0x360 net/nfc/nci/core.c:560
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #3 (&ndev->req_lock){+.+.}-{3:3}:
>        __mutex_lock_common kernel/locking/mutex.c:603 [inline]
>        __mutex_lock+0x124/0x83c kernel/locking/mutex.c:747
>        mutex_lock_nested+0x2c/0x40 kernel/locking/mutex.c:799
>        nci_request net/nfc/nci/core.c:148 [inline]
>        nci_set_local_general_bytes net/nfc/nci/core.c:774 [inline]
>        nci_start_poll+0x36c/0x624 net/nfc/nci/core.c:838
>        nfc_start_poll+0x114/0x270 net/nfc/core.c:225
>        nfc_genl_start_poll+0x154/0x3b0 net/nfc/netlink.c:828
>        genl_family_rcv_msg_doit+0x1b8/0x2a0 net/netlink/genetlink.c:756
>        genl_family_rcv_msg net/netlink/genetlink.c:833 [inline]
>        genl_rcv_msg+0x2f8/0x594 net/netlink/genetlink.c:850
>        netlink_rcv_skb+0x180/0x330 net/netlink/af_netlink.c:2540
>        genl_rcv+0x38/0x50 net/netlink/genetlink.c:861
>        netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
>        netlink_unicast+0x3ec/0x684 net/netlink/af_netlink.c:1345
>        netlink_sendmsg+0x690/0xb1c net/netlink/af_netlink.c:1921
>        sock_sendmsg_nosec net/socket.c:714 [inline]
>        sock_sendmsg+0xc0/0xf4 net/socket.c:734
>        ____sys_sendmsg+0x534/0x6b0 net/socket.c:2482
>        ___sys_sendmsg+0xf0/0x174 net/socket.c:2536
>        __sys_sendmsg+0xc4/0x154 net/socket.c:2565
>        __do_sys_sendmsg net/socket.c:2574 [inline]
>        __se_sys_sendmsg net/socket.c:2572 [inline]
>        __arm64_sys_sendmsg+0x70/0xa0 net/socket.c:2572
>        __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
>        invoke_syscall+0x6c/0x260 arch/arm64/kernel/syscall.c:52
>        el0_svc_common.constprop.0+0xc4/0x254 arch/arm64/kernel/syscall.c:142
>        do_el0_svc+0x50/0x14c arch/arm64/kernel/syscall.c:206
>        el0_svc+0x54/0x140 arch/arm64/kernel/entry-common.c:637
>        el0t_64_sync_handler+0xb8/0xc0 arch/arm64/kernel/entry-common.c:655
>        el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581
>
> -> #2 (&genl_data->genl_data_mutex){+.+.}-{3:3}:
>        __mutex_lock_common kernel/locking/mutex.c:603 [inline]
>        __mutex_lock+0x124/0x83c kernel/locking/mutex.c:747
>        mutex_lock_nested+0x2c/0x40 kernel/locking/mutex.c:799
>        nfc_urelease_event_work+0x118/0x270 net/nfc/netlink.c:1811
>        process_one_work+0x780/0x184c kernel/workqueue.c:2289
>        worker_thread+0x3cc/0xc40 kernel/workqueue.c:2436
>        kthread+0x23c/0x2a0 kernel/kthread.c:376
>        ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
>
> -> #1 (nfc_devlist_mutex){+.+.}-{3:3}:
>        __mutex_lock_common kernel/locking/mutex.c:603 [inline]
>        __mutex_lock+0x124/0x83c kernel/locking/mutex.c:747
>        mutex_lock_nested+0x2c/0x40 kernel/locking/mutex.c:799
>        nfc_register_device+0x34/0x320 net/nfc/core.c:1116
>        nci_register_device+0x604/0x8c0 net/nfc/nci/core.c:1256
>        virtual_ncidev_open+0x64/0xe0 drivers/nfc/virtual_ncidev.c:146
>        misc_open+0x294/0x394 drivers/char/misc.c:143
>        chrdev_open+0x1c0/0x54c fs/char_dev.c:414
>        do_dentry_open+0x3c4/0xf40 fs/open.c:882
>        vfs_open+0x90/0xd0 fs/open.c:1013
>        do_open fs/namei.c:3557 [inline]
>        path_openat+0x1030/0x1fe0 fs/namei.c:3713
>        do_filp_open+0x154/0x330 fs/namei.c:3740
>        do_sys_openat2+0x124/0x390 fs/open.c:1310
>        do_sys_open fs/open.c:1326 [inline]
>        __do_sys_openat fs/open.c:1342 [inline]
>        __se_sys_openat fs/open.c:1337 [inline]
>        __arm64_sys_openat+0x130/0x1c0 fs/open.c:1337
>        __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
>        invoke_syscall+0x6c/0x260 arch/arm64/kernel/syscall.c:52
>        el0_svc_common.constprop.0+0xc4/0x254 arch/arm64/kernel/syscall.c:142
>        do_el0_svc+0x50/0x14c arch/arm64/kernel/syscall.c:206
>        el0_svc+0x54/0x140 arch/arm64/kernel/entry-common.c:637
>        el0t_64_sync_handler+0xb8/0xc0 arch/arm64/kernel/entry-common.c:655
>        el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581
>
> -> #0 (nci_mutex){+.+.}-{3:3}:
>        check_prev_add kernel/locking/lockdep.c:3097 [inline]
>        check_prevs_add kernel/locking/lockdep.c:3216 [inline]
>        validate_chain kernel/locking/lockdep.c:3831 [inline]
>        __lock_acquire+0x2788/0x56d0 kernel/locking/lockdep.c:5055
>        lock_acquire kernel/locking/lockdep.c:5668 [inline]
>        lock_acquire+0x58c/0x9a0 kernel/locking/lockdep.c:5633
>        __mutex_lock_common kernel/locking/mutex.c:603 [inline]
>        __mutex_lock+0x124/0x83c kernel/locking/mutex.c:747
>        mutex_lock_nested+0x2c/0x40 kernel/locking/mutex.c:799
>        virtual_nci_close+0x2c/0x60 drivers/nfc/virtual_ncidev.c:44
>        nci_close_device+0x200/0x360 net/nfc/nci/core.c:592
>        nci_unregister_device+0x40/0x280 net/nfc/nci/core.c:1291
>        virtual_ncidev_close+0x70/0x90 drivers/nfc/virtual_ncidev.c:166
>        __fput+0x1ac/0x860 fs/file_table.c:320
>        ____fput+0x10/0x1c fs/file_table.c:348
>        task_work_run+0x12c/0x220 kernel/task_work.c:179
>        resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
>        do_notify_resume+0x920/0x2840 arch/arm64/kernel/signal.c:1127
>        prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
>        exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
>        el0_svc+0x11c/0x140 arch/arm64/kernel/entry-common.c:638
>        el0t_64_sync_handler+0xb8/0xc0 arch/arm64/kernel/entry-common.c:655
>        el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581
>
> other info that might help us debug this:
>
> Chain exists of:
>   nci_mutex --> &genl_data->genl_data_mutex --> &ndev->req_lock
>
>  Possible unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(&ndev->req_lock);
>                                lock(&genl_data->genl_data_mutex);
>                                lock(&ndev->req_lock);
>   lock(nci_mutex);
>
>  *** DEADLOCK ***
>
> 1 lock held by syz-executor.1/8551:
>  #0: ffff000030115350 (&ndev->req_lock){+.+.}-{3:3}, at: nci_close_device+0x5c/0x360 net/nfc/nci/core.c:560
>
> stack backtrace:
> CPU: 1 PID: 8551 Comm: syz-executor.1 Not tainted 6.1.0-rc4-syzkaller-00372-gaf7a05689189 #0
> Hardware name: linux,dummy-virt (DT)
> Call trace:
>  dump_backtrace+0xe0/0x140 arch/arm64/kernel/stacktrace.c:156
>  show_stack+0x18/0x40 arch/arm64/kernel/stacktrace.c:163
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x9c/0xd8 lib/dump_stack.c:106
>  dump_stack+0x1c/0x38 lib/dump_stack.c:113
>  print_circular_bug+0x2d4/0x2ec kernel/locking/lockdep.c:2055
>  check_noncircular+0x26c/0x2e0 kernel/locking/lockdep.c:2177
>  check_prev_add kernel/locking/lockdep.c:3097 [inline]
>  check_prevs_add kernel/locking/lockdep.c:3216 [inline]
>  validate_chain kernel/locking/lockdep.c:3831 [inline]
>  __lock_acquire+0x2788/0x56d0 kernel/locking/lockdep.c:5055
>  lock_acquire kernel/locking/lockdep.c:5668 [inline]
>  lock_acquire+0x58c/0x9a0 kernel/locking/lockdep.c:5633
>  __mutex_lock_common kernel/locking/mutex.c:603 [inline]
>  __mutex_lock+0x124/0x83c kernel/locking/mutex.c:747
>  mutex_lock_nested+0x2c/0x40 kernel/locking/mutex.c:799
>  virtual_nci_close+0x2c/0x60 drivers/nfc/virtual_ncidev.c:44
>  nci_close_device+0x200/0x360 net/nfc/nci/core.c:592
>  nci_unregister_device+0x40/0x280 net/nfc/nci/core.c:1291
>  virtual_ncidev_close+0x70/0x90 drivers/nfc/virtual_ncidev.c:166
>  __fput+0x1ac/0x860 fs/file_table.c:320
>  ____fput+0x10/0x1c fs/file_table.c:348
>  task_work_run+0x12c/0x220 kernel/task_work.c:179
>  resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
>  do_notify_resume+0x920/0x2840 arch/arm64/kernel/signal.c:1127
>  prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
>  exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
>  el0_svc+0x11c/0x140 arch/arm64/kernel/entry-common.c:638
>  el0t_64_sync_handler+0xb8/0xc0 arch/arm64/kernel/entry-common.c:655
>  el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581
>
>
> ---
> 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@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
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