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Or Har-Toov a44a3f175e RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency
Commit 51976c6cd7 ("RDMA/core: Provide rdma_user_mmap_disassociate()
to disassociate mmap pages") introduced disassociation_lock to protect
new mmap registrations against uverbs_user_mmap_disassociate(), but
created an ABBA deadlock:

  Thread A (mmap / fork):
    mmap_lock -> disassociation_lock

  Thread B (disassociate):
    disassociation_lock -> mmap_lock

Fix by removing disassociation_lock entirely and using the pre-existing
hw_destroy_rwsem instead. hw_destroy_rwsem already provides the same
protection: rdma_umap_open() and ib_uverbs_mmap() both use
down_read_trylock() before registering a new VMA, so holding hw_destroy_rwsem
in uverbs_user_mmap_disassociate() is sufficient to block new registrations.
trylock is used in both mmap paths (not blocking down_read) because
mmap_lock is already held on entry, and uverbs_user_mmap_disassociate()
acquires mmap_lock internally — a blocking read would recreate the same
deadlock.

The only caller that was not taking hw_destroy_rwsem for write was
rdma_user_mmap_disassociate(). Fix it to take the rwsem per-ufile while
iterating under lists_mutex.  This is safe because ib_uverbs_close()
releases hw_destroy_rwsem entirely before acquiring lists_mutex, so the
two locks are never held simultaneously.

lockdep warning:

 [  776.654252] ======================================================
 [  776.655214] WARNING: possible circular locking dependency detected
 [  776.656167] 6.18.0for-upstream_debug_94e244d9ccab #1 Not tainted
 [  776.657114] ------------------------------------------------------
 [  776.658087] devlink/14824 is trying to acquire lock:
 [  776.658879] ffff88811170c800 (&mm->mmap_lock){++++}-{4:4}, at: uverbs_user_mmap_disassociate+0x168/0x780 [ib_uverbs]
 [  776.660479]
 [  776.660479] but task is already holding lock:
 [  776.661460] ffff888142d92b08 (&file->disassociation_lock){+.+.}-{4:4}, at: uverbs_user_mmap_disassociate+0x39/0x780 [ib_uverbs]
 [  776.663177]
 [  776.663177] which lock already depends on the new lock.
 [  776.663177]
 [  776.664525]
 [  776.664525] the existing dependency chain (in reverse order) is:
 [  776.665724]
 [  776.665724] -> #2 (&file->disassociation_lock){+.+.}-{4:4}:
 [  776.666887]        __mutex_lock+0x16d/0x2330
 [  776.667633]        rdma_umap_open+0x129/0x280 [ib_uverbs]
 [  776.668489]        dup_mmap+0xa40/0x1790
 [  776.669170]        copy_process+0x5dd2/0x6170
 [  776.669933]        kernel_clone+0xb6/0x610
 [  776.670636]        __do_sys_clone+0xb5/0xf0
 [  776.671354]        do_syscall_64+0x70/0x12e0
 [  776.672083]        entry_SYSCALL_64_after_hwframe+0x4b/0x53
 [  776.672940]
 [  776.672940] -> #1 (&mm->mmap_lock/1){+.+.}-{4:4}:
 [  776.673985]        down_write_nested+0x90/0x1e0
 [  776.674751]        dup_mmap+0x201/0x1790
 [  776.675448]        copy_process+0x5dd2/0x6170
 [  776.676180]        kernel_clone+0xb6/0x610
 [  776.676904]        __do_sys_clone+0xb5/0xf0
 [  776.677615]        do_syscall_64+0x70/0x12e0
 [  776.678351]        entry_SYSCALL_64_after_hwframe+0x4b/0x53
 [  776.679239]
 [  776.679239] -> #0 (&mm->mmap_lock){++++}-{4:4}:
 [  776.680253]        __lock_acquire+0x18c6/0x2ec0
 [  776.681018]        lock_acquire+0x10e/0x2e0
 [  776.681742]        down_read+0x95/0x430
 [  776.682395]        uverbs_user_mmap_disassociate+0x168/0x780 [ib_uverbs]
 [  776.683436]        uverbs_destroy_ufile_hw+0x1ae/0x270 [ib_uverbs]
 [  776.684416]        ib_uverbs_remove_one+0x22b/0x420 [ib_uverbs]
 [  776.685371]        remove_client_context+0xa6/0xf0 [ib_core]
 [  776.686342]        disable_device+0x12b/0x240 [ib_core]
 [  776.687249]        __ib_unregister_device+0x269/0x460 [ib_core]
 [  776.688233]        ib_unregister_device+0x21/0x30 [ib_core]
 [  776.689140]        mlx5r_remove+0xd0/0x170 [mlx5_ib]
 [  776.689999]        device_release_driver_internal+0x3b2/0x560
 [  776.694876]        bus_remove_device+0x1f5/0x3e0
 [  776.695638]        device_del+0x3b9/0x990
 [  776.696329]        mlx5_detach_device+0x17e/0x350 [mlx5_core]
 [  776.697429]        mlx5_unload_one_devl_locked+0x3f/0xb0 [mlx5_core]
 [  776.698578]        mlx5_devlink_reload_down+0x1f9/0x550 [mlx5_core]
 [  776.699712]        devlink_reload+0x13e/0x680
 [  776.700456]        devlink_nl_reload_doit+0xc29/0x1160
 [  776.701293]        genl_family_rcv_msg_doit+0x1c9/0x2a0
 [  776.702135]        genl_rcv_msg+0x3f0/0x6b0
 [  776.702854]        netlink_rcv_skb+0x11d/0x370
 [  776.703605]        genl_rcv+0x24/0x40
 [  776.704236]        netlink_unicast+0x5b4/0x970
 [  776.704984]        netlink_sendmsg+0x730/0xbf0
 [  776.705748]        __sock_sendmsg+0xc5/0x190
 [  776.706461]        __sys_sendto+0x201/0x2f0
 [  776.707188]        __x64_sys_sendto+0xdc/0x1b0
 [  776.707931]        do_syscall_64+0x70/0x12e0
 [  776.708643]        entry_SYSCALL_64_after_hwframe+0x4b/0x53
 [  776.709546]
 [  776.709546] other info that might help us debug this:
 [  776.709546]
 [  776.710910] Chain exists of:
 [  776.710910]   &mm->mmap_lock --> &mm->mmap_lock/1 --> &file->disassociation_lock
 [  776.710910]
 [  776.712805]  Possible unsafe locking scenario:
 [  776.712805]
 [  776.713828]        CPU0                    CPU1
 [  776.714589]        ----                    ----
 [  776.715347]   lock(&file->disassociation_lock);
 [  776.716097]                                lock(&mm->mmap_lock/1);
 [  776.717067]                                lock(&file->disassociation_lock);
 [  776.718199]   rlock(&mm->mmap_lock);
 [  776.718857]
 [  776.718857]  *** DEADLOCK ***

Fixes: 51976c6cd7 ("RDMA/core: Provide rdma_user_mmap_disassociate() to disassociate mmap pages")
Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20260811-fix-mmap-lockdep-v1-1-1151b41063b4@nvidia.com
Acked-by: Junxian Huang <huangjunxian6@hisilicon.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
History 2026-09-01 10:03:08 -04:00
arch - Fix UM build regression caused by the removal of the UM 2026-08-30 10:19:11 -07:00
block for-7.3/block-20260819 2026-08-20 13:55:16 -07:00
certs treewide: fix indentation and whitespace in Kconfig files 2026-05-28 21:24:42 -07:00
crypto This push fixes a memory allocation overrun in crypto acomp. 2026-08-28 09:28:40 -07:00
Documentation Coccinelle patches for Linux v7.3 2026-08-30 10:42:40 -07:00
drivers RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency 2026-09-01 10:03:08 -04:00
fs tracing fixes for v7.3: 2026-08-30 09:22:00 -07:00
include RDMA/uverbs: Fix mmap_lock/disassociation_lock circular dependency 2026-09-01 10:03:08 -04:00
init Bootconfig updates for v7.3: 2026-08-25 08:59:09 -07:00
io_uring io_uring-7.3-20260828 2026-08-28 16:51:14 -07:00
ipc mm.git review status for master..mm-nonmm-stable 2026-08-23 08:07:11 -07:00
kernel - Revert a commit to spinlock cleanup guards that got caught up 2026-08-30 09:57:35 -07:00
lib mm.git review status for linus..mm-stable 2026-08-27 09:17:06 -07:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm mm.git review status for linus..mm-stable 2026-08-27 09:17:06 -07:00
net A wide variety of mostly CephFS fixes and cleanups, split between 2026-08-28 11:51:05 -07:00
rust Rust fixes for v7.3 2026-08-30 09:47:39 -07:00
samples tracing fixes for v7.3: 2026-08-30 09:22:00 -07:00
scripts Coccinelle patches for Linux v7.3 2026-08-30 10:42:40 -07:00
security Hi, 2026-08-28 09:36:27 -07:00
sound sound fixes for 7.3-rc1 2026-08-28 10:01:02 -07:00
tools Rust fixes for v7.3 2026-08-30 09:47:39 -07:00
usr usr: Correct a spelling by changing a letter 2026-08-05 14:51:58 +02:00
virt Arm: 2026-08-25 11:48:04 -07:00
.clang-format drm/bridge: rename drm_for_each_bridge_in_chain_scoped() to drm_for_each_bridge_in_chain() 2026-07-14 17:55:51 +02:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add Nathan Chancellor 2026-08-03 21:10:12 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore SPDX patches for 7.2-rc1 2026-06-22 12:06:22 -07:00
.mailmap CREDITS/mailmap: add some info about Darrick J. Wong 2026-08-30 10:29:08 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS/mailmap: add some info about Darrick J. Wong 2026-08-30 10:29:08 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS SCSI updates for 7.3 2026-08-29 11:55:36 -07:00
Makefile Linux 7.3-rc1 2026-08-30 13:34:40 -07:00
README README: remove out of place emdashes 2026-07-15 10:51:29 -06:00

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