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[104.199.160.21]) by smtp.gmail.com with UTF8SMTPSA id u2-20020a170902e80200b001b9da42cd7dsm7578243plg.279.2023.09.04.07.12.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 04 Sep 2023 07:12:05 -0700 (PDT) From: Ying Hsu To: linux-bluetooth@vger.kernel.org Cc: chromeos-bluetooth-upstreaming@chromium.org, Ying Hsu , Johan Hedberg , Luiz Augusto von Dentz , Marcel Holtmann , linux-kernel@vger.kernel.org Subject: [PATCH] Bluetooth: Fix hci_link_tx_to RCU lock usage Date: Mon, 4 Sep 2023 14:11:51 +0000 Message-ID: <20230904141155.1688673-1-yinghsu@chromium.org> X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org Syzbot found a bug "BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580". It is because hci_link_tx_to holds an RCU read lock and calls hci_disconnect which would hold a mutex lock since the commit a13f316e90fd ("Bluetooth: hci_conn: Consolidate code for aborting connections"). Here's an example call trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xfc/0x174 lib/dump_stack.c:106 ___might_sleep+0x4a9/0x4d3 kernel/sched/core.c:9663 __mutex_lock_common kernel/locking/mutex.c:576 [inline] __mutex_lock+0xc7/0x6e7 kernel/locking/mutex.c:732 hci_cmd_sync_queue+0x3a/0x287 net/bluetooth/hci_sync.c:388 hci_abort_conn+0x2cd/0x2e4 net/bluetooth/hci_conn.c:1812 hci_disconnect+0x207/0x237 net/bluetooth/hci_conn.c:244 hci_link_tx_to net/bluetooth/hci_core.c:3254 [inline] __check_timeout net/bluetooth/hci_core.c:3419 [inline] __check_timeout+0x310/0x361 net/bluetooth/hci_core.c:3399 hci_sched_le net/bluetooth/hci_core.c:3602 [inline] hci_tx_work+0xe8f/0x12d0 net/bluetooth/hci_core.c:3652 process_one_work+0x75c/0xba1 kernel/workqueue.c:2310 worker_thread+0x5b2/0x73a kernel/workqueue.c:2457 kthread+0x2f7/0x30b kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 This patch releases RCU read lock before calling hci_disconnect and reacquires it afterward to fix the bug. Fixes: a13f316e90fd ("Bluetooth: hci_conn: Consolidate code for aborting connections") Signed-off-by: Ying Hsu --- Tested this commit using a C reproducer on qemu-x86_64 for 10 minutes. net/bluetooth/hci_core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c index a5992f1b3c9b..db4f28d68d71 100644 --- a/net/bluetooth/hci_core.c +++ b/net/bluetooth/hci_core.c @@ -3418,7 +3418,12 @@ static void hci_link_tx_to(struct hci_dev *hdev, __u8 type) if (c->type == type && c->sent) { bt_dev_err(hdev, "killing stalled connection %pMR", &c->dst); + /* hci_disconnect might sleep, so, we have to release + * the RCU read lock before calling it. + */ + rcu_read_unlock(); hci_disconnect(c, HCI_ERROR_REMOTE_USER_TERM); + rcu_read_lock(); } }