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Rafael J. Wysocki cbd54987db cpufreq: Avoid using inconsistent policy->min and policy->max 
commit 7491cdf46b upstream.

Since cpufreq_driver_resolve_freq() can run in parallel with
cpufreq_set_policy() and there is no synchronization between them,
the former may access policy->min and policy->max while the latter
is updating them and it may see intermediate values of them due
to the way the update is carried out.  Also the compiler is free
to apply any optimizations it wants both to the stores in
cpufreq_set_policy() and to the loads in cpufreq_driver_resolve_freq()
which may result in additional inconsistencies.

To address this, use WRITE_ONCE() when updating policy->min and
policy->max in cpufreq_set_policy() and use READ_ONCE() for reading
them in cpufreq_driver_resolve_freq().  Moreover, rearrange the update
in cpufreq_set_policy() to avoid storing intermediate values in
policy->min and policy->max with the help of the observation that
their new values are expected to be properly ordered upfront.

Also modify cpufreq_driver_resolve_freq() to take the possible reverse
ordering of policy->min and policy->max, which may happen depending on
the ordering of operations when this function and cpufreq_set_policy()
run concurrently, into account by always honoring the max when it
turns out to be less than the min (in case it comes from thermal
throttling or similar).

Fixes: 1517176906 ("cpufreq: Make policy min/max hard requirements")
Cc: 5.16+ <stable@vger.kernel.org> # 5.16+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/5907080.DvuYhMxLoT@rjwysocki.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-05-09 09:43:53 +02:00
arch perf/x86/intel: KVM: Mask PEBS_ENABLE loaded for guest with vCPU's value. 2025-05-09 09:43:51 +02:00
block block: fix resource leak in blk_register_queue() error path 2025-04-25 10:45:42 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2025-04-25 10:45:58 +02:00
crypto crypto: null - Use spin lock instead of mutex 2025-05-02 07:50:52 +02:00
Documentation sched/topology: Consolidate and clean up access to a CPU's max compute capacity 2025-05-02 07:50:41 +02:00
drivers cpufreq: Avoid using inconsistent policy->min and policy->max 2025-05-09 09:43:53 +02:00
fs smb: client: fix zero length for mkdir POSIX create context 2025-05-09 09:43:53 +02:00
include sched/cpufreq: Rework schedutil governor performance estimation 2025-05-02 07:50:41 +02:00
init sched/isolation: Make CONFIG_CPU_ISOLATION depend on CONFIG_SMP 2025-05-02 07:50:57 +02:00
io_uring io_uring: always do atomic put from iowq 2025-05-02 07:50:57 +02:00
ipc ipc: fix memleak if msg_init_ns failed in create_ipc_ns 2024-12-09 10:32:54 +01:00
kernel tracing: Do not take trace_event_sem in print_event_fields() 2025-05-09 09:43:52 +02:00
lib ubsan: Fix panic from test_ubsan_out_of_bounds 2025-05-02 07:51:02 +02:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/memblock: repeat setting reserved region nid if array is doubled 2025-05-09 09:43:51 +02:00
net 9p/net: fix improper handling of bogus negative read/write replies 2025-05-02 07:50:56 +02:00
rust rust: lockdep: Remove support for dynamically allocated LockClassKeys 2025-03-22 12:50:50 -07:00
samples tracing: Verify event formats that have "%*p.." 2025-05-02 07:50:37 +02:00
scripts objtool: Silence more KCOV warnings, part 2 2025-05-02 07:51:04 +02:00
security landlock: Add the errata interface 2025-04-25 10:45:57 +02:00
sound ALSA: usb-audio: Add second USB ID for Jabra Evolve 65 headset 2025-05-09 09:43:49 +02:00
tools objtool: Ignore end-of-section jumps for KCOV/GCOV 2025-05-02 07:51:04 +02:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 12:58:38 +01:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.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 USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS sign-file,extract-cert: move common SSL helper functions to a header 2025-04-25 10:45:57 +02:00
Makefile Linux 6.6.89 2025-05-02 07:51:05 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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
``make pdfdocs``.  The formatted documentation can also be read online at:

    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.