syzbot found a potential circular dependency leading to a deadlock:
-> #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
-> #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: 92d4abd66f70 ("Bluetooth: vhci: Fix race when opening vhci device")
Signed-off-by: Ying Hsu <yinghsu@xxxxxxxxxxxx>
---
Tested this commit using a C reproducer on qemu-x86_64.
drivers/bluetooth/hci_vhci.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index f3892e9ce800..572d68d52965 100644
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -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>
@@ -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)
@@ -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;
}
@@ -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;
--
2.43.0.rc0.421.g78406f8d94-goog
