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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 commita13f316e90("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:a13f316e90("Bluetooth: hci_conn: Consolidate code for aborting connections") Signed-off-by: Ying Hsu <yinghsu@chromium.org> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.