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Bluetooth: Fix deadlock in vhci_send_frame
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syzbot found a potential circular dependency leading to a deadlock:
    -> virt-pvm#3 (&hdev->req_lock){+.+.}-{3:3}:
    __mutex_lock_common+0x1b6/0x1bc2 kernel/locking/mutex.c:599
    __mutex_lock kernel/locking/mutex.c:732 [inline]
    mutex_lock_nested+0x17/0x1c kernel/locking/mutex.c:784
    hci_dev_do_close+0x3f/0x9f net/bluetooth/hci_core.c:551
    hci_rfkill_set_block+0x130/0x1ac net/bluetooth/hci_core.c:935
    rfkill_set_block+0x1e6/0x3b8 net/rfkill/core.c:345
    rfkill_fop_write+0x2d8/0x672 net/rfkill/core.c:1274
    vfs_write+0x277/0xcf5 fs/read_write.c:594
    ksys_write+0x19b/0x2bd fs/read_write.c:650
    do_syscall_x64 arch/x86/entry/common.c:55 [inline]
    do_syscall_64+0x51/0xba arch/x86/entry/common.c:93
    entry_SYSCALL_64_after_hwframe+0x61/0xcb

    -> virt-pvm#2 (rfkill_global_mutex){+.+.}-{3:3}:
    __mutex_lock_common+0x1b6/0x1bc2 kernel/locking/mutex.c:599
    __mutex_lock kernel/locking/mutex.c:732 [inline]
    mutex_lock_nested+0x17/0x1c kernel/locking/mutex.c:784
    rfkill_register+0x30/0x7e3 net/rfkill/core.c:1045
    hci_register_dev+0x48f/0x96d net/bluetooth/hci_core.c:2622
    __vhci_create_device drivers/bluetooth/hci_vhci.c:341 [inline]
    vhci_create_device+0x3ad/0x68f drivers/bluetooth/hci_vhci.c:374
    vhci_get_user drivers/bluetooth/hci_vhci.c:431 [inline]
    vhci_write+0x37b/0x429 drivers/bluetooth/hci_vhci.c:511
    call_write_iter include/linux/fs.h:2109 [inline]
    new_sync_write fs/read_write.c:509 [inline]
    vfs_write+0xaa8/0xcf5 fs/read_write.c:596
    ksys_write+0x19b/0x2bd fs/read_write.c:650
    do_syscall_x64 arch/x86/entry/common.c:55 [inline]
    do_syscall_64+0x51/0xba arch/x86/entry/common.c:93
    entry_SYSCALL_64_after_hwframe+0x61/0xcb

    -> #1 (&data->open_mutex){+.+.}-{3:3}:
    __mutex_lock_common+0x1b6/0x1bc2 kernel/locking/mutex.c:599
    __mutex_lock kernel/locking/mutex.c:732 [inline]
    mutex_lock_nested+0x17/0x1c kernel/locking/mutex.c:784
    vhci_send_frame+0x68/0x9c drivers/bluetooth/hci_vhci.c:75
    hci_send_frame+0x1cc/0x2ff net/bluetooth/hci_core.c:2989
    hci_sched_acl_pkt net/bluetooth/hci_core.c:3498 [inline]
    hci_sched_acl net/bluetooth/hci_core.c:3583 [inline]
    hci_tx_work+0xb94/0x1a60 net/bluetooth/hci_core.c:3654
    process_one_work+0x901/0xfb8 kernel/workqueue.c:2310
    worker_thread+0xa67/0x1003 kernel/workqueue.c:2457
    kthread+0x36a/0x430 kernel/kthread.c:319
    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

    -> #0 ((work_completion)(&hdev->tx_work)){+.+.}-{0:0}:
    check_prev_add kernel/locking/lockdep.c:3053 [inline]
    check_prevs_add kernel/locking/lockdep.c:3172 [inline]
    validate_chain kernel/locking/lockdep.c:3787 [inline]
    __lock_acquire+0x2d32/0x77fa kernel/locking/lockdep.c:5011
    lock_acquire+0x273/0x4d5 kernel/locking/lockdep.c:5622
    __flush_work+0xee/0x19f kernel/workqueue.c:3090
    hci_dev_close_sync+0x32f/0x1113 net/bluetooth/hci_sync.c:4352
    hci_dev_do_close+0x47/0x9f net/bluetooth/hci_core.c:553
    hci_rfkill_set_block+0x130/0x1ac net/bluetooth/hci_core.c:935
    rfkill_set_block+0x1e6/0x3b8 net/rfkill/core.c:345
    rfkill_fop_write+0x2d8/0x672 net/rfkill/core.c:1274
    vfs_write+0x277/0xcf5 fs/read_write.c:594
    ksys_write+0x19b/0x2bd fs/read_write.c:650
    do_syscall_x64 arch/x86/entry/common.c:55 [inline]
    do_syscall_64+0x51/0xba arch/x86/entry/common.c:93
    entry_SYSCALL_64_after_hwframe+0x61/0xcb

This change removes the need for acquiring the open_mutex in
vhci_send_frame, thus eliminating the potential deadlock while
maintaining the required packet ordering.

Fixes: 92d4abd ("Bluetooth: vhci: Fix race when opening vhci device")
Signed-off-by: Ying Hsu <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
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@Vudentz
Ying Hsu authored and Vudentz committed Dec 15, 2023
1 parent f67eabf commit 769bf60
Showing 1 changed file with 6 additions and 4 deletions.
10 changes: 6 additions & 4 deletions drivers/bluetooth/hci_vhci.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
#include <linux/module.h>
#include <asm/unaligned.h>

#include <linux/atomic.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/slab.h>
Expand Down Expand Up @@ -44,6 +45,7 @@ struct vhci_data {
bool wakeup;
__u16 msft_opcode;
bool aosp_capable;
atomic_t initialized;
};

static int vhci_open_dev(struct hci_dev *hdev)
Expand Down Expand Up @@ -75,11 +77,10 @@ static int vhci_send_frame(struct hci_dev *hdev, struct sk_buff *skb)

memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1);

mutex_lock(&data->open_mutex);
skb_queue_tail(&data->readq, skb);
mutex_unlock(&data->open_mutex);

wake_up_interruptible(&data->read_wait);
if (atomic_read(&data->initialized))
wake_up_interruptible(&data->read_wait);
return 0;
}

Expand Down Expand Up @@ -464,7 +465,8 @@ static int __vhci_create_device(struct vhci_data *data, __u8 opcode)
skb_put_u8(skb, 0xff);
skb_put_u8(skb, opcode);
put_unaligned_le16(hdev->id, skb_put(skb, 2));
skb_queue_tail(&data->readq, skb);
skb_queue_head(&data->readq, skb);
atomic_inc(&data->initialized);

wake_up_interruptible(&data->read_wait);
return 0;
Expand Down

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