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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Pull fsnotify updates from Jan Kara:
"A couple of small fsnotify fixes and cleanups"
* tag 'fsnotify_for_v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
fanotify: replace deprecated strcpy in fanotify_info_copy_{name,name2}
fsnotify: inotify: pass mark connector to fsnotify_recalc_mask()
fanotify: call fanotify_events_supported() before path_permission() and security_path_notify()
fanotify: avoid/silence premature LSM capability checks
inotify: fix watch count leak when fsnotify_add_inode_mark_locked() fails
Pull smb server updates from Steve French:
- smbdirect double free fixes
- Add some smbdirect logging
- Minor cleanup in crypto, and smbdirect and in IPC handling
- Minor cleanup to move header info to common FSCC code
- Fix crypt message use after free
- Fix memory leak in session setup
- Fix for DACL parsing
- Fix EA name length validation
- Reconnect fix
- Fix use after free in close
* tag 'v7.1-rc-part1-ksmbd-srv-fixes' of git://git.samba.org/ksmbd:
smb: smbdirect: add some logging to SMBDIRECT_CHECK_STATUS_{WARN,DISCONNECT}()
smb: smbdirect: introduce smbdirect_socket.logging infrastructure
smb: smbdirect: let smbdirect.h include #include <linux/types.h>
smb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list()
smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()
ksmbd: fix use-after-free from async crypto on Qualcomm crypto engine
ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc
ksmbd: require 3 sub-authorities before reading sub_auth[2]
ksmbd: validate EaNameLength in smb2_get_ea()
ksmbd: Remove unnecessary selection of CRYPTO_ECB
ksmbd: validate owner of durable handle on reconnect
ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger
ksmbd: ipc: use kzalloc_flex and __counted_by
smb: move filesystem_vol_info into common/fscc.h
smb: move file_basic_info into common/fscc.h
smb: move some definitions from common/smb2pdu.h into common/fscc.h
strcpy() has been deprecated [1] because it performs no bounds checking
on the destination buffer, which can lead to buffer overflows. Replace
it with the safer strscpy().
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [1]
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20260321210544.519259-4-thorsten.blum@linux.dev
Signed-off-by: Jan Kara <jack@suse.cz>
Pull gfs2 updates from Andreas Gruenbacher:
- Fix possible data loss during inode evict
- Fix a race during bufdata allocation
- More careful cleaning up during a withdraw
- Prevent excessive log flushing under memory pressure
- Various other minor fixes and cleanups
* tag 'gfs2-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
gfs2: prevent NULL pointer dereference during unmount
gfs2: hide error messages after withdraw
gfs2: wait for withdraw earlier during unmount
gfs2: inode directory consistency checks
gfs2: gfs2_log_flush withdraw fixes
gfs2: add some missing log locking
gfs2: fix address space truncation during withdraw
gfs2: drain ail under sd_log_flush_lock
gfs2: bufdata allocation race
gfs2: Remove trans_drain code duplication
gfs2: Move gfs2_remove_from_journal to log.c
gfs2: Get rid of gfs2_log_[un]lock helpers
gfs2: less aggressive low-memory log flushing
gfs2: Fix data loss during inode evict
gfs2: minor evict_[un]linked_inode cleanup
gfs2: Avoid unnecessary transactions in evict_linked_inode
gfs2: Remove unnecessary check in gfs2_evict_inode
gfs2: Call unlock_new_inode before d_instantiate
This should make it easier to analyze any possible problems.
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
fsnotify_recalc_mask() expects a plain struct fsnotify_mark_connector *,
but inode->i_fsnotify_marks is an __rcu pointer. Use fsn_mark->connector
instead to avoid sparse "different address spaces" warnings.
Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
Link: https://patch.msgid.link/20260214051217.1381363-1-sun.jian.kdev@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
Pull fuse update from Miklos Szeredi:
- Fix possible hang in virtiofs when cleaning up a DAX inode (Sergio
Lopez)
- Fix a warning when using large folio as the source of SPLICE_F_MOVE
on the fuse device (Bernd)
- Fix uninitialized value found by KMSAN (Luis Henriques)
- Fix synchronous INIT hang (Miklos)
- Fix race between inode initialization and FUSE_NOTIFY_INVAL_INODE
(Horst)
- Allow fd to be closed after passing fuse device fd to
fsconfig(..., "fd", ...) (Miklos)
- Support FSCONFIG_SET_FD for "fd" option (Miklos)
- Misc fixes and cleanups
* tag 'fuse-update-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse: (21 commits)
fuse: support FSCONFIG_SET_FD for "fd" option
fuse: clean up device cloning
fuse: don't require /dev/fuse fd to be kept open during mount
fuse: add refcount to fuse_dev
fuse: create fuse_dev on /dev/fuse open instead of mount
fuse: check connection state on notification
fuse: fuse_dev_ioctl_clone() should wait for device file to be initialized
fuse: fix inode initialization race
fuse: abort on fatal signal during sync init
fuse: fix uninit-value in fuse_dentry_revalidate()
fuse: use offset_in_page() for page offset calculations
fuse: use DIV_ROUND_UP() for page count calculations
fuse: simplify logic in fuse_notify_store() and fuse_retrieve()
fuse: validate outarg offset and size in notify store/retrieve
fuse: Check for large folio with SPLICE_F_MOVE
fuse: quiet down complaints in fuse_conn_limit_write
fuse: drop unnecessary argument from fuse_lookup_init()
fuse: fix premature writetrhough request for large folio
fuse: refactor duplicate queue teardown operation
virtiofs: add FUSE protocol validation
...
When flushing out outstanding glock work during an unmount, gfs2_log_flush()
can be called when sdp->sd_jdesc has already been deallocated and sdp->sd_jdesc
is NULL. Commit 35264909e9d1 ("gfs2: Fix NULL pointer dereference in
gfs2_log_flush") added a check for that to gfs2_log_flush() itself, but it
missed the sdp->sd_jdesc dereference in gfs2_log_release(). Fix that.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202604071139.HNJiCaAi-lkp@intel.com/
Fixes: 35264909e9d1 ("gfs2: Fix NULL pointer dereference in gfs2_log_flush")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This will be used by client and server in order to keep controlling
the logging when we move to shared functions.
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
The latter trigger LSM (e.g. SELinux) checks, which will log a denial
when permission is denied, so it's better to do them after validity
checks to avoid logging a denial when the operation would fail anyway.
Fixes: 0b3b094ac9a7 ("fanotify: Disallow permission events for proc filesystem")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Paul Moore <paul@paul-moore.com>
Link: https://patch.msgid.link/20260216150625.793013-3-omosnace@redhat.com
Signed-off-by: Jan Kara <jack@suse.cz>
Pull RTLA updates from Steven Rostedt:
- Simplify option parsing
Auto-generate getopt_long() optstring for short options from long
options array, avoiding the need to specify it manually and reducing
the surface for mistakes.
- Add unit tests
Implement unit tests (make unit-tests) using libcheck, next to
existing runtime tests (make check). Currently, three functions from
utils.c are tested.
- Add --stack-format option
In addition to stopping stack pointer decoding (with -s/--stack
option) on first unresolvable pointer, allow also skipping
unresolvable pointers and displaying everything, configurable with a
new option.
- Unify number of CPUs into one global variable
Use one global variable, nr_cpus, to store the number of CPUs instead
of retrieving it and passing it at multiple places.
- Fix behavior in various corner cases
Make RTLA behave correctly in several corner cases: memory allocation
failure, invalid value read from kernel side, thread creation
failure, malformed time value input, and read/write failure or
interruption by signal.
- Improve string handling
Simplify several places in the code that handle strings, including
parsing of action arguments. A few new helper functions and variables
are added for that purpose.
- Get rid of magic numbers
Few places handling paths use a magic number of 1024. Replace it with
MAX_PATH and ARRAY_SIZE() macro.
- Unify threshold handling
Code that handles response to latency threshold is duplicated between
tools, which has led to bugs in the past. Unify it into a new helper
as much as possible.
- Fix segfault on SIGINT during cleanup
The SIGINT handler touches dynamically allocated memory. Detach it
before freeing it during cleanup to prevent segmentation fault and
discarding of output buffers. Also, properly document SIGINT handling
while at it.
* tag 'trace-rtla-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (28 commits)
Documentation/rtla: Document SIGINT behavior
rtla: Fix segfault on multiple SIGINTs
rtla/utils: Fix loop condition in PID validation
rtla/utils: Fix resource leak in set_comm_sched_attr()
rtla/trace: Fix I/O handling in save_trace_to_file()
rtla/trace: Fix write loop in trace_event_save_hist()
rtla/timerlat: Simplify RTLA_NO_BPF environment variable check
rtla: Use str_has_prefix() for option prefix check
rtla: Enforce exact match for time unit suffixes
rtla: Use str_has_prefix() for prefix checks
rtla: Add str_has_prefix() helper function
rtla: Handle pthread_create() failure properly
rtla/timerlat: Add bounds check for softirq vector
rtla: Simplify code by caching string lengths
rtla: Replace magic number with MAX_PATH
rtla: Introduce common_threshold_handler() helper
rtla/actions: Simplify argument parsing
rtla: Use strdup() to simplify code
rtla: Exit on memory allocation failures during initialization
tools/rtla: Remove unneeded nr_cpus from for_each_monitored_cpu
...
This is not only cleaner to use in userspace (no need to sprintf the fd to
a string) but also allows userspace to detect that the devfd can be closed
after the fsconfig call.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
In gfs2_evict_inode(), don't issue error messages once a withdraw has already
occurred.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This will make it easier to use.
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Make sure calling capable()/ns_capable() actually leads to access denied
when false is returned, because these functions emit an audit record
when a Linux Security Module denies the capability, which makes it
difficult to avoid allowing/silencing unnecessary permissions in
security policies (namely with SELinux).
Where the return value just used to set a flag, use the non-auditing
ns_capable_noaudit() instead.
Fixes: 7cea2a3c505e ("fanotify: support limited functionality for unprivileged users")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Link: https://patch.msgid.link/20260216150625.793013-2-omosnace@redhat.com
Signed-off-by: Jan Kara <jack@suse.cz>
Pull runtime verification updates from Steven Rostedt:
- Refactor da_monitor header to share handlers across monitor types
No functional changes, only less code duplication.
- Add Hybrid Automata model class
Add a new model class that extends deterministic automata by adding
constraints on transitions and states. Those constraints can take
into account wall-clock time and as such allow RV monitor to make
assertions on real time. Add documentation and code generation
scripts.
- Add stall monitor as hybrid automaton example
Add a monitor that triggers a violation when a task is stalling as an
example of automaton working with real time variables.
- Convert the opid monitor to a hybrid automaton
The opid monitor can be heavily simplified if written as a hybrid
automaton: instead of tracking preempt and interrupt enable/disable
events, it can just run constraints on the preemption/interrupt
states when events like wakeup and need_resched verify.
- Add support for per-object monitors in DA/HA
Allow writing deterministic and hybrid automata monitors for generic
objects (e.g. any struct), by exploiting a hash table where objects
are saved. This allows to track more than just tasks in RV. For
instance it will be used to track deadline entities in deadline
monitors.
- Add deadline tracepoints and move some deadline utilities
Prepare the ground for deadline monitors by defining events and
exporting helpers.
- Add nomiss deadline monitor
Add first example of deadline monitor asserting all entities complete
before their deadline.
- Improve rvgen error handling
Introduce AutomataError exception class and better handle expected
exceptions while showing a backtrace for unexpected ones.
- Improve python code quality in rvgen
Refactor the rvgen generation scripts to align with python best
practices: use f-strings instead of %, use len() instead of
__len__(), remove semicolons, use context managers for file
operations, fix whitespace violations, extract magic strings into
constants, remove unused imports and methods.
- Fix small bugs in rvgen
The generator scripts presented some corner case bugs: logical error
in validating what a correct dot file looks like, fix an isinstance()
check, enforce a dot file has an initial state, fix type annotations
and typos in comments.
- rvgen refactoring
Refactor automata.py to use iterator-based parsing and handle
required arguments directly in argparse.
- Allow epoll in rtapp-sleep monitor
The epoll_wait call is now rt-friendly so it should be allowed in the
sleep monitor as a valid sleep method.
* tag 'trace-rv-v7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (32 commits)
rv: Allow epoll in rtapp-sleep monitor
rv/rvgen: fix _fill_states() return type annotation
rv/rvgen: fix unbound loop variable warning
rv/rvgen: enforce presence of initial state
rv/rvgen: extract node marker string to class constant
rv/rvgen: fix isinstance check in Variable.expand()
rv/rvgen: make monitor arguments required in rvgen
rv/rvgen: remove unused __get_main_name method
rv/rvgen: remove unused sys import from dot2c
rv/rvgen: refactor automata.py to use iterator-based parsing
rv/rvgen: use class constant for init marker
rv/rvgen: fix DOT file validation logic error
rv/rvgen: fix PEP 8 whitespace violations
rv/rvgen: fix typos in automata and generator docstring and comments
rv/rvgen: use context managers for file operations
rv/rvgen: remove unnecessary semicolons
rv/rvgen: replace __len__() calls with len()
rv/rvgen: replace % string formatting with f-strings
rv/rvgen: remove bare except clauses in generator
rv/rvgen: introduce AutomataError exception class
...