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[34.80.137.231]) by smtp.gmail.com with UTF8SMTPSA id a6-20020a170902ee8600b001c0a4146961sm1470983pld.19.2023.11.03.07.21.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Nov 2023 07:21:33 -0700 (PDT) From: Ying Hsu To: linux-bluetooth@vger.kernel.org Cc: luiz.dentz@gmail.com, linux-kernel@vger.kernel.org, chromeos-bluetooth-upstreaming@chromium.org, Ying Hsu Subject: [PATCH] Bluetooth: Fix deadlock in vhci_send_frame Date: Fri, 3 Nov 2023 14:21:26 +0000 Message-ID: <20231103142126.3847457-1-yinghsu@chromium.org> X-Mailer: git-send-email 2.42.0.869.gea05f2083d-goog MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 --- 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 #include =20 +#include #include #include #include @@ -44,6 +45,7 @@ struct vhci_data { bool wakeup; __u16 msft_opcode; bool aosp_capable; + atomic_t initialized; }; =20 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) =20 memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1); =20 - mutex_lock(&data->open_mutex); skb_queue_tail(&data->readq, skb); - mutex_unlock(&data->open_mutex); =20 - wake_up_interruptible(&data->read_wait); + if (atomic_read(&data->initialized)) + wake_up_interruptible(&data->read_wait); return 0; } =20 @@ -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); =20 wake_up_interruptible(&data->read_wait); return 0; --=20 2.42.0.869.gea05f2083d-goog