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    Subject[PATCH 5.19 0528/1157] Bluetooth: When HCI work queue is drained, only queue chained work
    Date
    From: Schspa Shi <schspa@gmail.com>

    [ Upstream commit 877afadad2dce8aae1f2aad8ce47e072d4f6165e ]

    The HCI command, event, and data packet processing workqueue is drained
    to avoid deadlock in commit
    76727c02c1e1 ("Bluetooth: Call drain_workqueue() before resetting state").

    There is another delayed work, which will queue command to this drained
    workqueue. Which results in the following error report:

    Bluetooth: hci2: command 0x040f tx timeout
    WARNING: CPU: 1 PID: 18374 at kernel/workqueue.c:1438 __queue_work+0xdad/0x1140
    Workqueue: events hci_cmd_timeout
    RIP: 0010:__queue_work+0xdad/0x1140
    RSP: 0000:ffffc90002cffc60 EFLAGS: 00010093
    RAX: 0000000000000000 RBX: ffff8880b9d3ec00 RCX: 0000000000000000
    RDX: ffff888024ba0000 RSI: ffffffff814e048d RDI: ffff8880b9d3ec08
    RBP: 0000000000000008 R08: 0000000000000000 R09: 00000000b9d39700
    R10: ffffffff814f73c6 R11: 0000000000000000 R12: ffff88807cce4c60
    R13: 0000000000000000 R14: ffff8880796d8800 R15: ffff8880796d8800
    FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 000000c0174b4000 CR3: 000000007cae9000 CR4: 00000000003506e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    <TASK>
    ? queue_work_on+0xcb/0x110
    ? lockdep_hardirqs_off+0x90/0xd0
    queue_work_on+0xee/0x110
    process_one_work+0x996/0x1610
    ? pwq_dec_nr_in_flight+0x2a0/0x2a0
    ? rwlock_bug.part.0+0x90/0x90
    ? _raw_spin_lock_irq+0x41/0x50
    worker_thread+0x665/0x1080
    ? process_one_work+0x1610/0x1610
    kthread+0x2e9/0x3a0
    ? kthread_complete_and_exit+0x40/0x40
    ret_from_fork+0x1f/0x30
    </TASK>

    To fix this, we can add a new HCI_DRAIN_WQ flag, and don't queue the
    timeout workqueue while command workqueue is draining.

    Fixes: 76727c02c1e1 ("Bluetooth: Call drain_workqueue() before resetting state")
    Reported-by: syzbot+63bed493aebbf6872647@syzkaller.appspotmail.com
    Signed-off-by: Schspa Shi <schspa@gmail.com>
    Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/net/bluetooth/hci.h | 1 +
    net/bluetooth/hci_core.c | 10 +++++++++-
    net/bluetooth/hci_event.c | 5 +++--
    3 files changed, 13 insertions(+), 3 deletions(-)

    diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
    index fe7935be7dc4..4a45c48eb0d2 100644
    --- a/include/net/bluetooth/hci.h
    +++ b/include/net/bluetooth/hci.h
    @@ -361,6 +361,7 @@ enum {
    HCI_QUALITY_REPORT,
    HCI_OFFLOAD_CODECS_ENABLED,
    HCI_LE_SIMULTANEOUS_ROLES,
    + HCI_CMD_DRAIN_WORKQUEUE,

    __HCI_NUM_FLAGS,
    };
    diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
    index a0f99baafd35..6a53bcc5cfbb 100644
    --- a/net/bluetooth/hci_core.c
    +++ b/net/bluetooth/hci_core.c
    @@ -594,6 +594,11 @@ static int hci_dev_do_reset(struct hci_dev *hdev)
    skb_queue_purge(&hdev->rx_q);
    skb_queue_purge(&hdev->cmd_q);

    + /* Cancel these to avoid queueing non-chained pending work */
    + hci_dev_set_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE);
    + cancel_delayed_work(&hdev->cmd_timer);
    + cancel_delayed_work(&hdev->ncmd_timer);
    +
    /* Avoid potential lockdep warnings from the *_flush() calls by
    * ensuring the workqueue is empty up front.
    */
    @@ -607,6 +612,8 @@ static int hci_dev_do_reset(struct hci_dev *hdev)
    if (hdev->flush)
    hdev->flush(hdev);

    + hci_dev_clear_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE);
    +
    atomic_set(&hdev->cmd_cnt, 1);
    hdev->acl_cnt = 0; hdev->sco_cnt = 0; hdev->le_cnt = 0;

    @@ -3864,7 +3871,8 @@ static void hci_cmd_work(struct work_struct *work)
    if (res < 0)
    __hci_cmd_sync_cancel(hdev, -res);

    - if (test_bit(HCI_RESET, &hdev->flags))
    + if (test_bit(HCI_RESET, &hdev->flags) ||
    + hci_dev_test_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE))
    cancel_delayed_work(&hdev->cmd_timer);
    else
    schedule_delayed_work(&hdev->cmd_timer,
    diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
    index af17dfb20e01..7cb956d3abb2 100644
    --- a/net/bluetooth/hci_event.c
    +++ b/net/bluetooth/hci_event.c
    @@ -3768,8 +3768,9 @@ static inline void handle_cmd_cnt_and_timer(struct hci_dev *hdev, u8 ncmd)
    cancel_delayed_work(&hdev->ncmd_timer);
    atomic_set(&hdev->cmd_cnt, 1);
    } else {
    - schedule_delayed_work(&hdev->ncmd_timer,
    - HCI_NCMD_TIMEOUT);
    + if (!hci_dev_test_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE))
    + schedule_delayed_work(&hdev->ncmd_timer,
    + HCI_NCMD_TIMEOUT);
    }
    }
    }
    --
    2.35.1


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