Sungwoo Kim 0f8a5dcc66 Bluetooth: sco: Fix a race condition in sco_sock_timeout()
sco_sock_timeout() runs asynchronously and lock_sock(sk). If the socket
is closing while the timer is running, it holds the same lock
(lock_sock(sk)) twice, leading to a deadlock.

CPU 0                      CPU 1
====================       ======================
sco_sock_close()
                           sco_sock_timeout()
lock_sock(sk) // <-- LOCK
  __sco_sock_close()
    sco_chan_del()
      sco_conn_put()
	      sco_conn_free()
	        disable_delayed_work_sync()
	                           lock(sk) // <-- SAME LOCK

Fix this by moving disable_delayed_work_sync() outside of lock_sock(sk),
ensuring that no lock_sock(sk) is held before sco_sock_timeout().

Lockdep splat:

WARNING: possible circular locking dependency detected
6.13.0-rc4 #7 Not tainted

syz-executor292/9514 is trying to acquire lock:
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: rcu_lock_acquire sect/v6.13-rc4/./include/linux/rcupdate.h:337 [inline]
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: rcu_read_lock sect/v6.13-rc4/./include/linux/rcupdate.h:849 [inline]
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: start_flush_work sect/v6.13-rc4/kernel/workqueue.c:4137 [inline]
ffff8881115d5070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: __flush_work+0xd1/0xc40 sect/v6.13-rc4/kernel/workqueue.c:4195

but task is already holding lock:
ffff88807db3a258 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: lock_sock sect/v6.13-rc4/./include/net/sock.h:1623 [inline]
ffff88807db3a258 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_sock_close+0x25/0x100 sect/v6.13-rc4/net/bluetooth/sco.c:524

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       lock_acquire+0x1c4/0x520 sect/v6.13-rc4/kernel/locking/lockdep.c:5849
       lock_sock_nested+0x48/0x130 sect/v6.13-rc4/net/core/sock.c:3622
       lock_sock sect/v6.13-rc4/./include/net/sock.h:1623 [inline]
       sco_sock_timeout+0xbe/0x270 sect/v6.13-rc4/net/bluetooth/sco.c:158
       process_one_work sect/v6.13-rc4/kernel/workqueue.c:3229 [inline]
       process_scheduled_works+0xa99/0x18f0 sect/v6.13-rc4/kernel/workqueue.c:3310
       worker_thread+0x8a9/0xd80 sect/v6.13-rc4/kernel/workqueue.c:3391
       kthread+0x2c6/0x360 sect/v6.13-rc4/kernel/kthread.c:389
       ret_from_fork+0x4e/0x80 sect/v6.13-rc4/arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 sect/v6.13-rc4/arch/x86/entry/entry_64.S:244

-> #0 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}:
       check_prev_add sect/v6.13-rc4/kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add sect/v6.13-rc4/kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x1888/0x5760 sect/v6.13-rc4/kernel/locking/lockdep.c:3904
       __lock_acquire+0x13b4/0x2120 sect/v6.13-rc4/kernel/locking/lockdep.c:5226
       lock_acquire+0x1c4/0x520 sect/v6.13-rc4/kernel/locking/lockdep.c:5849
       touch_work_lockdep_map sect/v6.13-rc4/kernel/workqueue.c:3909 [inline]
       start_flush_work sect/v6.13-rc4/kernel/workqueue.c:4163 [inline]
       __flush_work+0x70f/0xc40 sect/v6.13-rc4/kernel/workqueue.c:4195
       __cancel_work_sync sect/v6.13-rc4/kernel/workqueue.c:4351 [inline]
       disable_delayed_work_sync+0xbb/0xf0 sect/v6.13-rc4/kernel/workqueue.c:4514
       sco_conn_free sect/v6.13-rc4/net/bluetooth/sco.c:95 [inline]
       kref_put sect/v6.13-rc4/./include/linux/kref.h:65 [inline]
       sco_conn_put+0x18f/0x270 sect/v6.13-rc4/net/bluetooth/sco.c:107
       sco_chan_del+0xe2/0x210 sect/v6.13-rc4/net/bluetooth/sco.c:236
       sco_sock_close+0x8f/0x100 sect/v6.13-rc4/net/bluetooth/sco.c:526
       sco_sock_release+0x62/0x2d0 sect/v6.13-rc4/net/bluetooth/sco.c:1300
       __sock_release+0xe1/0x2d0 sect/v6.13-rc4/net/socket.c:640
       sock_close+0x1c/0x30 sect/v6.13-rc4/net/socket.c:1408
       __fput+0x2bd/0xa80 sect/v6.13-rc4/fs/file_table.c:450
       __fput_sync+0x15e/0x1c0 sect/v6.13-rc4/fs/file_table.c:535
       __do_sys_close sect/v6.13-rc4/fs/open.c:1554 [inline]
       __se_sys_close sect/v6.13-rc4/fs/open.c:1539 [inline]
       __x64_sys_close+0x93/0x120 sect/v6.13-rc4/fs/open.c:1539
       do_syscall_x64 sect/v6.13-rc4/arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xee/0x210 sect/v6.13-rc4/arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: e6720779ae ("Bluetooth: SCO: Use kref to track lifetime of sco_conn")
Acked-by: Dave Tian <daveti@purdue.edu>
Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
2026-07-06 10:46:57 -04:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2026-06-28 12:01:31 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst
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