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 vfs fixes from Christian Brauner:
- kthread: consolidate kthread exit paths to prevent use-after-free
- iomap:
- don't mark folio uptodate if read IO has bytes pending
- don't report direct-io retries to fserror
- reject delalloc mappings during writeback
- ns: tighten visibility checks
- netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict
sequence
* tag 'vfs-7.0-rc3.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
iomap: reject delalloc mappings during writeback
iomap: don't mark folio uptodate if read IO has bytes pending
selftests: fix mntns iteration selftests
nstree: tighten permission checks for listing
nsfs: tighten permission checks for handle opening
nsfs: tighten permission checks for ns iteration ioctls
netfs: Fix unbuffered/DIO writes to dispatch subrequests in strict sequence
kthread: consolidate kthread exit paths to prevent use-after-free
iomap: don't report direct-io retries to fserror
Pull sysctl fix from Joel Granados:
- Fix error when reporting jiffies converted values back to user space
Return the converted value instead of "Invalid argument" error
* tag 'sysctl-7.00-fixes-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
time/jiffies: Fix sysctl file error on configurations where USER_HZ < HZ
Filesystems should never provide a delayed allocation mapping to
writeback; they're supposed to allocate the space before replying.
This can lead to weird IO errors and crashes in the block layer if the
filesystem is being malicious, or if it hadn't set iomap->dev because
it's a delalloc mapping.
Fix this by failing writeback on delalloc mappings. Currently no
filesystems actually misbehave in this manner, but we ought to be
stricter about things like that.
Cc: stable@vger.kernel.org # v5.5
Fixes: 598ecfbaa742ac ("iomap: lift the xfs writeback code to iomap")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://patch.msgid.link/20260302173002.GL13829@frogsfrogsfrogs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Pull media fix from Mauro Carvalho Chehab:
"Fix for MPEG-TS decoder in dvb-net"
* tag 'media/v7.0-3' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
media: dvb-net: fix OOB access in ULE extension header tables
Commit 2dc164a48e6fd ("sysctl: Create converter functions with two new
macros") incorrectly returns error to user space when jiffies sysctl
converter is used. The old overflow check got replaced with an
unconditional one:
+ if (USER_HZ < HZ)
+ return -EINVAL;
which will always be true on configurations with "USER_HZ < HZ".
Remove the check; it is no longer needed as clock_t_to_jiffies() returns
ULONG_MAX for the overflow case and proc_int_u2k_conv_uop() checks for
"> INT_MAX" after conversion
Fixes: 2dc164a48e6fd ("sysctl: Create converter functions with two new macros")
Reported-by: Colm Harrington <colm.harrington@oracle.com>
Signed-off-by: Gerd Rausch <gerd.rausch@oracle.com>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
Joanne Koong <joannelkoong@gmail.com> says:
This is a fix for this scenario:
->read_folio() gets called on a folio size that is 16k while the file is 4k:
a) ifs->read_bytes_pending gets initialized to 16k
b) ->read_folio_range() is called for the 4k read
c) the 4k read succeeds, ifs->read_bytes_pending is now 12k and the
0 to 4k range is marked uptodate
d) the post-eof blocks are zeroed and marked uptodate in the call to
iomap_set_range_uptodate()
e) iomap_set_range_uptodate() sees all the ranges are marked
uptodate and it marks the folio uptodate
f) iomap_read_end() gets called to subtract the 12k from
ifs->read_bytes_pending. it too sees all the ranges are marked
uptodate and marks the folio uptodate using XOR
g) the XOR call clears the uptodate flag on the folio
The same situation can occur if the last range read for the folio is done as
an inline read and all the previous ranges have already completed by the time
the inline read completes.
For more context, the full discussion can be found in [1]. There was a
discussion about alternative approaches in that thread, but they had more
complications.
There is another discussion in v1 [2] about consolidating the read paths.
Until that is resolved, this patch fixes the issue.
[1] https://lore.kernel.org/linux-fsdevel/CAJnrk1Z9za5w4FoJqTGx50zR2haHHaoot1KJViQyEHJQq4=34w@mail.gmail.com/#t
[2] https://lore.kernel.org/linux-fsdevel/20260219003911.344478-1-joannelkoong@gmail.com/T/#u
* patches from https://patch.msgid.link/20260303233420.874231-1-joannelkoong@gmail.com:
iomap: don't mark folio uptodate if read IO has bytes pending
Link: https://patch.msgid.link/20260303233420.874231-1-joannelkoong@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Pull pin control fixes from Linus Walleij:
"All of these are driver fixes except a memory leak in the
pinconf_generic_parse_dt_config() helper which is the most
important fix.
- Rename and fix up the Intel Equilibrium immutable interrupt chip
- Handle the Qualcomm QCS615 dual edge GPIO IRQ by adding the right
flag
- Fix a memory leak in the widely used pinconf_generic_parse_dt_config()
and a more local leak in aml_dt_node_to_map_pinmux()
- Fix double put in the Cirrus cs42l43_pin_probe()
- Staticize amdisp_pinctrl_ops, Qualcomm SDM660 groups and functions
- Unexport CIX sky1_pinctrl_pm_ops
- Fix configuration of deferred pin in the Rockchip driver
- Implement .get_direction() in the Sunxi driver squelching a dmesg
warning message
- Fix a readout of the last bank of registers in the Cypress CY8C95x0
driver"
* tag 'pinctrl-v7.0-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
pinctrl: cy8c95x0: Don't miss reading the last bank registers
pinctrl: sunxi: Implement gpiochip::get_direction()
pinctrl: rockchip: Fix configuring a deferred pin
pinctrl: cirrus: cs42l43: Fix double-put in cs42l43_pin_probe()
pinctrl: meson: amlogic-a4: Fix device node reference leak in aml_dt_node_to_map_pinmux()
pinctrl: qcom: sdm660-lpass-lpi: Make groups and functions variables static
pinctrl: cix: sky1: Unexport sky1_pinctrl_pm_ops
pinctrl: amdisp: Make amdisp_pinctrl_ops variable static
pinctrl: pinconf-generic: Fix memory leak in pinconf_generic_parse_dt_config()
pinctrl: qcom: qcs615: Add missing dual edge GPIO IRQ errata flag
pinctrl: equilibrium: fix warning trace on load
pinctrl: equilibrium: rename irq_chip function callbacks
The ule_mandatory_ext_handlers[] and ule_optional_ext_handlers[] tables
in handle_one_ule_extension() are declared with 255 elements (valid
indices 0-254), but the index htype is derived from network-controlled
data as (ule_sndu_type & 0x00FF), giving a range of 0-255. When
htype equals 255, an out-of-bounds read occurs on the function pointer
table, and the OOB value may be called as a function pointer.
Add a bounds check on htype against the array size before either table
is accessed. Out-of-range values now cause the SNDU to be discarded.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Ariel Silver <arielsilver77@gmail.com>
Signed-off-by: Ariel Silver <arielsilver77@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Christian Brauner <brauner@kernel.org> says:
Listing various namespaces is currently only scoped on owning namespace.
We can make this more fine-grained so that we scope visibility even
tighter. To make it possible to change behavior restrict visibility for
now. This shouldn't be a big deal as there aren't actual large users out
there and paves the way to make this even cleaner in the future.
* patches from https://patch.msgid.link/20260226-work-visibility-fixes-v1-0-d2c2853313bd@kernel.org:
selftests: fix mntns iteration selftests
nstree: tighten permission checks for listing
nsfs: tighten permission checks for handle opening
nsfs: tighten permission checks for ns iteration ioctls
Link: https://patch.msgid.link/20260226-work-visibility-fixes-v1-0-d2c2853313bd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
If a folio has ifs metadata attached to it and the folio is partially
read in through an async IO helper with the rest of it then being read
in through post-EOF zeroing or as inline data, and the helper
successfully finishes the read first, then post-EOF zeroing / reading
inline will mark the folio as uptodate in iomap_set_range_uptodate().
This is a problem because when the read completion path later calls
iomap_read_end(), it will call folio_end_read(), which sets the uptodate
bit using XOR semantics. Calling folio_end_read() on a folio that was
already marked uptodate clears the uptodate bit.
Fix this by not marking the folio as uptodate if the read IO has bytes
pending. The folio uptodate state will be set in the read completion
path through iomap_end_read() -> folio_end_read().
Reported-by: Wei Gao <wegao@suse.com>
Suggested-by: Sasha Levin <sashal@kernel.org>
Tested-by: Wei Gao <wegao@suse.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: stable@vger.kernel.org # v6.19
Link: https://lore.kernel.org/linux-fsdevel/aYbmy8JdgXwsGaPP@autotest-wegao.qe.prg2.suse.org/
Fixes: b2f35ac4146d ("iomap: add caller-provided callbacks for read and readahead")
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://patch.msgid.link/20260303233420.874231-2-joannelkoong@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Pull cgroup fixes from Tejun Heo:
- Fix circular locking dependency in cpuset partition code by
deferring housekeeping_update() calls to a workqueue instead
of calling them directly under cpus_read_lock
- Fix null-ptr-deref in rebuild_sched_domains_cpuslocked() when
generate_sched_domains() returns NULL due to kmalloc failure
- Fix incorrect cpuset behavior for effective_xcpus in
partition_xcpus_del() and cpuset_update_tasks_cpumask()
in update_cpumasks_hier()
- Fix race between task migration and cgroup iteration
* tag 'cgroup-for-7.0-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: fix null-ptr-deref in rebuild_sched_domains_cpuslocked
cgroup/cpuset: Call housekeeping_update() without holding cpus_read_lock
cgroup/cpuset: Defer housekeeping_update() calls from CPU hotplug to workqueue
cgroup/cpuset: Move housekeeping_update()/rebuild_sched_domains() together
kselftest/cgroup: Simplify test_cpuset_prs.sh by removing "S+" command
cgroup/cpuset: Set isolated_cpus_updating only if isolated_cpus is changed
cgroup/cpuset: Clarify exclusion rules for cpuset internal variables
cgroup/cpuset: Fix incorrect use of cpuset_update_tasks_cpumask() in update_cpumasks_hier()
cgroup/cpuset: Fix incorrect change to effective_xcpus in partition_xcpus_del()
cgroup: fix race between task migration and iteration
When code had been changed to use for_each_set_clump8(), it mistakenly
switched from chip->nport to chip->tpin since the cy8c9540 and cy8c9560
have a 4-pin gap. This, in particular, led to the missed read of
the last bank interrupt status register and hence missing interrupts
on those pins. Restore the upper limit in for_each_set_clump8() to take
into consideration that gap.
Fixes: 83e29a7a1fdf ("pinctrl: cy8c95x0; Switch to use for_each_set_clump8()")
Cc: stable@vger.kernel.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>
Pull kvm fixes from Paolo Bonzini:
"Arm:
- Make sure we don't leak any S1POE state from guest to guest when
the feature is supported on the HW, but not enabled on the host
- Propagate the ID registers from the host into non-protected VMs
managed by pKVM, ensuring that the guest sees the intended feature
set
- Drop double kern_hyp_va() from unpin_host_sve_state(), which could
bite us if we were to change kern_hyp_va() to not being idempotent
- Don't leak stage-2 mappings in protected mode
- Correctly align the faulting address when dealing with single page
stage-2 mappings for PAGE_SIZE > 4kB
- Fix detection of virtualisation-capable GICv5 IRS, due to the
maintainer being obviously fat fingered... [his words, not mine]
- Remove duplication of code retrieving the ASID for the purpose of
S1 PT handling
- Fix slightly abusive const-ification in vgic_set_kvm_info()
Generic:
- Remove internal Kconfigs that are now set on all architectures
- Remove per-architecture code to enable KVM_CAP_SYNC_MMU, all
architectures finally enable it in Linux 7.0"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: always define KVM_CAP_SYNC_MMU
KVM: remove CONFIG_KVM_GENERIC_MMU_NOTIFIER
KVM: arm64: Deduplicate ASID retrieval code
irqchip/gic-v5: Fix inversion of IRS_IDR0.virt flag
KVM: arm64: Revert accidental drop of kvm_uninit_stage2_mmu() for non-NV VMs
KVM: arm64: Fix protected mode handling of pages larger than 4kB
KVM: arm64: vgic: Handle const qualifier from gic_kvm_info allocation type
KVM: arm64: Remove redundant kern_hyp_va() in unpin_host_sve_state()
KVM: arm64: Fix ID register initialization for non-protected pKVM guests
KVM: arm64: Optimise away S1POE handling when not supported by host
KVM: arm64: Hide S1POE from guests when not supported by the host
Fix netfslib such that when it's making an unbuffered or DIO write, to make
sure that it sends each subrequest strictly sequentially, waiting till the
previous one is 'committed' before sending the next so that we don't have
pieces landing out of order and potentially leaving a hole if an error
occurs (ENOSPC for example).
This is done by copying in just those bits of issuing, collecting and
retrying subrequests that are necessary to do one subrequest at a time.
Retrying, in particular, is simpler because if the current subrequest needs
retrying, the source iterator can just be copied again and the subrequest
prepped and issued again without needing to be concerned about whether it
needs merging with the previous or next in the sequence.
Note that the issuing loop waits for a subrequest to complete right after
issuing it, but this wait could be moved elsewhere allowing preparatory
steps to be performed whilst the subrequest is in progress. In particular,
once content encryption is available in netfslib, that could be done whilst
waiting, as could cleanup of buffers that have been completed.
Fixes: 153a9961b551 ("netfs: Implement unbuffered/DIO write support")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://patch.msgid.link/58526.1772112753@warthog.procyon.org.uk
Tested-by: Steve French <sfrench@samba.org>
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>