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
Pull SCSI fixes from James Bottomley:
"Small changes in drivers only, no core changes.
The firewire one fixes a user controlled overflow (but I still can't
see how it could be exploited)"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: ufs: amd-versal2: Fix PHY initialization in HCE enable notify
scsi: firewire: sbp-target: Fix overflow in sbp_make_tpg()
scsi: be2iscsi: Fix a memory leak in beiscsi_boot_get_sinfo()
scsi: qla2xxx: edif: Fix dma_free_coherent() size
Pull perf events fix from Ingo Molnar:
"Fix a race in the user-callchains code"
* tag 'perf-urgent-2026-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: sched: Fix perf crash with new is_user_task() helper
Move the PHY initialization from PRE_CHANGE to POST_CHANGE in the
ufs_versal2_hce_enable_notify() callback. This ensures that the PHY is
initialized after the host controller enable sequence is complete, rather
than before it starts.
The PHY initialization requires the UFS host controller to be in a stable
enabled state to properly configure the MPHY registers. Moving this to
POST_CHANGE aligns with the expected initialization order and prevents
potential timing issues during controller startup.
Fixes: 769b8b2ffded ("scsi: ufs: amd-versal2: Add UFS support for AMD Versal Gen 2 SoC")
Signed-off-by: Ajay Neeli <ajay.neeli@amd.com>
Link: https://patch.msgid.link/20251224053950.54213-1-ajay.neeli@amd.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Pull scheduler fix from Ingo Molnar:
"Fix a regression in the deferrable dl_server code that can cause the
dl_server to be stuck"
* tag 'sched-urgent-2026-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/deadline: Fix 'stuck' dl_server
In order to do a user space stacktrace the current task needs to be a user
task that has executed in user space. It use to be possible to test if a
task is a user task or not by simply checking the task_struct mm field. If
it was non NULL, it was a user task and if not it was a kernel task.
But things have changed over time, and some kernel tasks now have their
own mm field.
An idea was made to instead test PF_KTHREAD and two functions were used to
wrap this check in case it became more complex to test if a task was a
user task or not[1]. But this was rejected and the C code simply checked
the PF_KTHREAD directly.
It was later found that not all kernel threads set PF_KTHREAD. The io-uring
helpers instead set PF_USER_WORKER and this needed to be added as well.
But checking the flags is still not enough. There's a very small window
when a task exits that it frees its mm field and it is set back to NULL.
If perf were to trigger at this moment, the flags test would say its a
user space task but when perf would read the mm field it would crash with
at NULL pointer dereference.
Now there are flags that can be used to test if a task is exiting, but
they are set in areas that perf may still want to profile the user space
task (to see where it exited). The only real test is to check both the
flags and the mm field.
Instead of making this modification in every location, create a new
is_user_task() helper function that does all the tests needed to know if
it is safe to read the user space memory or not.
[1] https://lore.kernel.org/all/20250425204120.639530125@goodmis.org/
Fixes: 90942f9fac05 ("perf: Use current->flags & PF_KTHREAD|PF_USER_WORKER instead of current->mm == NULL")
Closes: https://lore.kernel.org/all/0d877e6f-41a7-4724-875d-0b0a27b8a545@roeck-us.net/
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260129102821.46484722@gandalf.local.home
The code in sbp_make_tpg() limits "tpgt" to UINT_MAX but the data type of
"tpg->tport_tpgt" is u16. This causes a type truncation issue.
When a user creates a TPG via configfs mkdir, for example:
mkdir /sys/kernel/config/target/sbp/<wwn>/tpgt_70000
The value 70000 passes the "tpgt > UINT_MAX" check since 70000 is far less
than 4294967295. However, when assigned to the u16 field tpg->tport_tpgt,
the value is silently truncated to 4464 (70000 & 0xFFFF). This causes the
value the user specified to differ from what is actually stored, leading to
confusion and potential unexpected behavior.
Fix this by changing the type of "tpgt" to u16 and using kstrtou16() which
will properly reject values outside the u16 range.
Fixes: a511ce339780 ("sbp-target: Initial merge of firewire/ieee-1394 target mode support")
Signed-off-by: Kery Qi <qikeyu2017@gmail.com>
Link: https://patch.msgid.link/20260121114515.1829-2-qikeyu2017@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Pull objtool fixes from Ingo Molnar:
- Fix a build error on ia32-x86_64 cross builds
- Replace locally open coded ALIGN_UP(), ALIGN_UP_POW2()
and MAX(), which, beyond being duplicates, the
ALIGN_UP_POW2() is also buggy
- Fix objtool klp-diff regression caused by a recent
change to the bug table format
- Fix klp-build vs CONFIG_MODULE_SRCVERSION_ALL build
failure
* tag 'objtool-urgent-2026-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
livepatch/klp-build: Fix klp-build vs CONFIG_MODULE_SRCVERSION_ALL
objtool/klp: Fix bug table handling for __WARN_printf()
objtool: Replace custom macros in elf.c with shared ones
objtool: Print bfd_vma as unsigned long long on ia32-x86_64 cross build
Andrea reported the dl_server getting stuck for him. He tracked it
down to a state where dl_server_start() saw dl_defer_running==1, but
the dl_server's job is no longer valid at the time of
dl_server_start().
In the state diagram this corresponds to [4] D->A (or dl_server_stop()
due to no more runnable tasks) followed by [1], which in case of a
lapsed deadline must then be A->B.
Now our A has dl_defer_running==1, while B demands
dl_defer_running==0, therefore it must get cleared when the CBS wakeup
rules demand a replenish.
Fixes: a110a81c52a9 ("sched/deadline: Deferrable dl server")
Reported-by: Andrea Righi arighi@nvidia.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Tested-by: Andrea Righi arighi@nvidia.com
Link: https://lkml.kernel.org/r/20260123161645.2181752-1-arighi@nvidia.com
Link: https://patch.msgid.link/20260130124100.GC1079264@noisy.programming.kicks-ass.net
If nonemb_cmd->va fails to be allocated, free the allocation previously
made by alloc_mcc_wrb().
Fixes: 50a4b824be9e ("scsi: be2iscsi: Fix to make boot discovery non-blocking")
Cc: stable@vger.kernel.org
Signed-off-by: Haoxiang Li <lihaoxiang@isrc.iscas.ac.cn>
Link: https://patch.msgid.link/20251213083643.301240-1-lihaoxiang@isrc.iscas.ac.cn
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Pull irq fixes from Ingo Molnar:
"Misc irqchip fixes:
- Fix a regression in the ls-extirq irqchip driver
- Fix an irqchip platform enumeration regression
in the simple-pm-bus driver"
* tag 'irq-urgent-2026-02-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
bus: simple-pm-bus: Probe the Layerscape SCFG node
irqchip/ls-extirq: Convert to a platform driver to make it work again
When building a patch to a single-file kernel module with
CONFIG_MODULE_SRCVERSION_ALL enabled, the klp-build module link fails in
modpost:
Diffing objects
drivers/md/raid0.o: changed function: raid0_run
Building patch module: livepatch-0001-patch-raid0_run.ko
drivers/md/raid0.c: No such file or directory
...
The problem here is that klp-build copied drivers/md/.raid0.o.cmd to the
module build directory, but it didn't also copy over the input source
file listed in the .cmd file:
source_drivers/md/raid0.o := drivers/md/raid0.c
So modpost dies due to the missing .c file which is needed for
calculating checksums for CONFIG_MODULE_SRCVERSION_ALL.
Instead of copying the original .cmd file, just create an empty one.
Modpost only requires that it exists. The original object's build
dependencies are irrelevant for the frankenobjects used by klp-build.
Fixes: 24ebfcd65a87 ("livepatch/klp-build: Introduce klp-build script for generating livepatch modules")
Reported-by: Song Liu <song@kernel.org>
Tested-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/c41b6629e02775e4c1015259aa36065b3fe2f0f3.1769471792.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Pull SCSI fixes from James Bottomley:
"Only one core change, the rest are drivers.
The core change reorders some state operations in the error handler to
try to prevent missed wake ups of the error handler (which can halt
error processing and effectively freeze the entire system)"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: qla2xxx: Sanitize payload size to prevent member overflow
scsi: target: iscsi: Fix use-after-free in iscsit_dec_session_usage_count()
scsi: target: iscsi: Fix use-after-free in iscsit_dec_conn_usage_count()
scsi: core: Wake up the error handler when final completions race against each other
scsi: storvsc: Process unsupported MODE_SENSE_10
scsi: xen: scsiback: Fix potential memory leak in scsiback_remove()
Earlier in the function, the ha->flt buffer is allocated with size
sizeof(struct qla_flt_header) + FLT_REGIONS_SIZE but freed in the error
path with size SFP_DEV_SIZE.
Fixes: 84318a9f01ce ("scsi: qla2xxx: edif: Add send, receive, and accept for auth_els")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Fourier <fourier.thomas@gmail.com>
Link: https://patch.msgid.link/20260112134326.55466-2-fourier.thomas@gmail.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Pull iommu fixes from Joerg Roedel:
- Fix a performance regression cause by the new Generic IO-Page-Table
code detected in Intel VT-d driver
- Command queue flushing fix for NVidia version of the ARM-SMMU-v3
* tag 'iommu-fixes-v6.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/iommu/linux:
iommu/tegra241-cmdqv: Reset VCMDQ in tegra241_vcmdq_hw_init_user()
iommupt: Only cache flush memory changed by unmap
Make the simple-pm-bus driver probe the Layerscape SCFG dt nodes and
populate platform_device structures from its child dt nodes.
This is now needed because its child interrupt-controller - ls-extirq -
is being handled as a platform_device instead of being initialized
through the IRQCHIP_DECLARE infrastructure which impeded its parent IRQ
retrieval through the blamed commit.
Note that this does not set ONLY_BUS because that enables the
of_platform_populate() call. The extra power management operations which
are enabled by that are not required but harmless.
Fixes: 1b1f04d8271e ("of/irq: Ignore interrupt parent for nodes without interrupts")
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20260122134034.3274053-3-ioana.ciornei@nxp.com