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 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 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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Pull ceph updates from Ilya Dryomov:
"We have a patch that adds an initial set of tracepoints to the MDS
client from Max, a fix that hardens osdmap parsing code from myself
(marked for stable) and a few assorted fixups"
* tag 'ceph-for-6.19-rc1' of https://github.com/ceph/ceph-client:
rbd: stop selecting CRC32, CRYPTO, and CRYPTO_AES
ceph: stop selecting CRC32, CRYPTO, and CRYPTO_AES
libceph: make decode_pool() more resilient against corrupted osdmaps
libceph: Amend checking to fix `make W=1` build breakage
ceph: Amend checking to fix `make W=1` build breakage
ceph: add trace points to the MDS client
libceph: fix log output race condition in OSD client
Pull tomoyo update from Tetsuo Handa:
"Trivial optimization"
* tag 'tomoyo-pr-20251212' of git://git.code.sf.net/p/tomoyo/tomoyo:
tomoyo: Use local kmap in tomoyo_dump_page()
None of the RBD code directly requires CRC32, CRYPTO, or CRYPTO_AES.
These options are needed by CEPH_LIB code and they are selected there
directly.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@linux.dev>
Pull CPU hotplug fix from Ingo Molnar:
- Fix CPU hotplug callbacks to disable interrupts on UP kernels
* tag 'smp-urgent-2025-12-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
cpu: Make atomic hotplug callbacks run with interrupts disabled on UP
Replace the now deprecated kmap_atomic() with kmap_local_page().
The memcpy does not need atomic semantics, and the removed comment
is now stale - this patch now makes it in sync again. Last but not
least, highmem is going to be removed[0].
Link: https://lore.kernel.org/all/4ff89b72-03ff-4447-9d21-dd6a5fe1550f@app.fastmail.com/ [0]
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
None of the CEPH_FS code directly requires CRC32, CRYPTO, or CRYPTO_AES.
These options do get selected indirectly anyway via CEPH_LIB, which does
need them, but there is no need for CEPH_FS to select them too.
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Pull perf event fixes from Ingo Molnar:
- Fix NULL pointer dereference crash in the Intel PMU driver
- Fix missing read event generation on task exit
- Fix AMD uncore driver init error handling
- Fix whitespace noise
* tag 'perf-urgent-2025-12-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/intel: Fix NULL event dereference crash in handle_pmi_common()
perf/core: Fix missing read event generation on task exit
perf/x86/amd/uncore: Fix the return value of amd_uncore_df_event_init() on error
perf/uprobes: Remove <space><Tab> whitespace noise
On SMP systems the CPU hotplug callbacks in the "starting" range are
invoked while the CPU is brought up and interrupts are still
disabled. Callbacks which are added later are invoked via the
hotplug-thread on the target CPU and interrupts are explicitly disabled.
In the UP case callbacks which are added later are invoked directly without
the thread indirection. This is in principle okay since there is just one
CPU but those callbacks are invoked with interrupt disabled code. That's
incorrect as those callbacks assume interrupt disabled context.
Disable interrupts before invoking the callbacks on UP if the state is
atomic and interrupts are expected to be disabled. The "save" part is
required because this is also invoked early in the boot process while
interrupts are disabled and must not be enabled prematurely.
Fixes: 06ddd17521bf1 ("sched/smp: Always define is_percpu_thread() and scheduler_ipi()")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://patch.msgid.link/20251127144723.ev9DuXXR@linutronix.de
If the osdmap is (maliciously) corrupted such that the encoded length
of ceph_pg_pool envelope is less than what is expected for a particular
encoding version, out-of-bounds reads may ensue because the only bounds
check that is there is based on that length value.
This patch adds explicit bounds checks for each field that is decoded
or skipped.
Cc: stable@vger.kernel.org
Reported-by: ziming zhang <ezrakiez@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Tested-by: ziming zhang <ezrakiez@gmail.com>
Pull irq fixes from Ingo Molnar:
- Fix error code in the irqchip/mchp-eic driver
- Fix setup_percpu_irq() affinity assumptions
- Remove the unused irq_domain_add_tree() function
* tag 'irq-urgent-2025-12-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irqchip/mchp-eic: Fix error code in mchp_eic_domain_alloc()
irqdomain: Delete irq_domain_add_tree()
genirq: Allow NULL affinity for setup_percpu_irq()
handle_pmi_common() may observe an active bit set in cpuc->active_mask
while the corresponding cpuc->events[] entry has already been cleared,
which leads to a NULL pointer dereference.
This can happen when interrupt throttling stops all events in a group
while PEBS processing is still in progress. perf_event_overflow() can
trigger perf_event_throttle_group(), which stops the group and clears
the cpuc->events[] entry, but the active bit may still be set when
handle_pmi_common() iterates over the events.
The following recent fix:
7e772a93eb61 ("perf/x86: Fix NULL event access and potential PEBS record loss")
moved the cpuc->events[] clearing from x86_pmu_stop() to x86_pmu_del() and
relied on cpuc->active_mask/pebs_enabled checks. However,
handle_pmi_common() can still encounter a NULL cpuc->events[] entry
despite the active bit being set.
Add an explicit NULL check on the event pointer before using it,
to cover this legitimate scenario and avoid the NULL dereference crash.
Fixes: 7e772a93eb61 ("perf/x86: Fix NULL event access and potential PEBS record loss")
Reported-by: kitta <kitta@linux.alibaba.com>
Co-developed-by: kitta <kitta@linux.alibaba.com>
Signed-off-by: Evan Li <evan.li@linux.alibaba.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20251212084943.2124787-1-evan.li@linux.alibaba.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220855
Pull f2fs updates from Jaegeuk Kim:
"This series focuses on minor clean-ups and performance optimizations
across sysfs, documentation, debugfs, tracepoints, slab allocation,
and GC. Furthermore, it resolves several corner-case bugs caught by
xfstests, as well as issues related to 16KB page support and
f2fs_enable_checkpoint.
Enhancement:
- wrap ASCII tables in literal blocks to fix LaTeX build
- optimize trace_f2fs_write_checkpoint with enums
- support to show curseg.next_blkoff in debugfs
- add a sysfs entry to show max open zones
- add fadvise tracepoint
- use global inline_xattr_slab instead of per-sb slab cache
- set default valid_thresh_ratio to 80 for zoned devices
- maintain one time GC mode is enabled during whole zoned GC cycle
Bug fix:
- ensure node page reads complete before f2fs_put_super() finishes
- do not account invalid blocks in get_left_section_blocks()
- revert summary entry count from 2048 to 512 in 16kb block support
- detect recoverable inode during dryrun of find_fsync_dnodes()
- fix age extent cache insertion skip on counter overflow
- add sanity checks before unlinking and loading inodes
- ensure minimum trim granularity accounts for all devices
- block cache/dio write during f2fs_enable_checkpoint()
- propagate error from f2fs_enable_checkpoint()
- invalidate dentry cache on failed whiteout creation
- avoid updating compression context during writeback
- avoid updating zero-sized extent in extent cache
- avoid potential deadlock"
* tag 'f2fs-for-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (39 commits)
f2fs: ignore discard return value
f2fs: optimize trace_f2fs_write_checkpoint with enums
f2fs: fix to not account invalid blocks in get_left_section_blocks()
f2fs: support to show curseg.next_blkoff in debugfs
docs: f2fs: wrap ASCII tables in literal blocks to fix LaTeX build
f2fs: expand scalability of f2fs mount option
f2fs: change default schedule timeout value
f2fs: introduce f2fs_schedule_timeout()
f2fs: use memalloc_retry_wait() as much as possible
f2fs: add a sysfs entry to show max open zones
f2fs: wrap all unusable_blocks_per_sec code in CONFIG_BLK_DEV_ZONED
f2fs: simplify list initialization in f2fs_recover_fsync_data()
f2fs: revert summary entry count from 2048 to 512 in 16kb block support
f2fs: fix to detect recoverable inode during dryrun of find_fsync_dnodes()
f2fs: fix return value of f2fs_recover_fsync_data()
f2fs: add fadvise tracepoint
f2fs: fix age extent cache insertion skip on counter overflow
f2fs: Add sanity checks before unlinking and loading inodes
f2fs: Rename f2fs_unlink exit label
f2fs: ensure minimum trim granularity accounts for all devices
...
Pull timer fix from Borislav Petkov:
- Have timekeeping aux clocks sysfs interface setup function return an
error code on failure instead of success
* tag 'timers_urgent_for_v6.18_rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timekeeping: Fix error code in tk_aux_sysfs_init()
In a few cases the code compares 32-bit value to a SIZE_MAX derived
constant which is much higher than that value on 64-bit platforms,
Clang, in particular, is not happy about this
net/ceph/osdmap.c:1441:10: error: result of comparison of constant 4611686018427387891 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
1441 | if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
| ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/ceph/osdmap.c:1624:10: error: result of comparison of constant 2305843009213693945 with expression of type 'u32' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
1624 | if (len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
| ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fix this by casting to size_t. Note, that possible replacement of SIZE_MAX
by U32_MAX may lead to the behaviour changes on the corner cases.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Pull misc core fixes from Ingo Molnar:
- Improve bug reporting
- Suppress W=1 format warning
- Improve rseq scalability on Clang builds
* tag 'core-urgent-2025-12-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rseq: Always inline rseq_debug_syscall_return()
bug: Hush suggest-attribute=format for __warn_printf()
bug: Let report_bug_entry() provide the correct bugaddr
If irq_domain_translate_twocell() sets "hwirq" to >= MCHP_EIC_NIRQ (2) then
it results in an out of bounds access.
The code checks for invalid values, but doesn't set the error code. Return
-EINVAL in that case, instead of returning success.
Fixes: 00fa3461c86d ("irqchip/mchp-eic: Add support for the Microchip EIC")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Link: https://patch.msgid.link/aTfHmOz6IBpTIPU5@stanley.mountain