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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kmod.c was originally introduced in the kernel in February
of 1998 by Linus Torvalds - who was familiar with kernel
licensing at the time this was introduced.
Signed-off-by: Tim Bird <tim.bird@sony.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull ftrace fix from Steven Rostedt:
- Fix allocation accounting on boot up
The ftrace records for each function that ftrace can attach to is
done in a group of pages. At boot up, the number of pages are
calculated and allocated. After that, the pages are filled with data.
It may allocate more than needed due to some functions not being
recorded (because they are unused weak functions), this too is
recorded.
After the data is filled in, a check is made to make sure the right
number of pages were allocated. But this was off due to the
assumption that the same number of entries fit per every page.
Because the size of an entry does not evenly divide into PAGE_SIZE,
there is a rounding error when a large number of pages is allocated
to hold the events. This causes the check to fail and triggers a
warning.
Fix the accounting by finding out how many pages are actually
allocated from the functions that allocate them and use that to see
if all the pages allocated were used and the ones not used are
properly freed.
* tag 'ftrace-v6.19-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
ftrace: Do not over-allocate ftrace memory
Pull NFS client fixes from Trond Myklebust:
- Fix another deadlock involving nfs_release_folio()
- localio:
- Stop I/O upon hitting a fatal error
- Deal with page offsets that are > PAGE_SIZE
- Fix size read races in truncate, fallocate and copy offload
- Several bugfixes for the NFSv4.x directory delegation client code
- pNFS:
- Fix a deadlock when returning delegations during open
- Fix memory leaks in various error paths
* tag 'nfs-for-6.19-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
NFS: Fix size read races in truncate, fallocate and copy offload
NFS: Don't immediately return directory delegations when disabled
NFS/localio: Deal with page bases that are > PAGE_SIZE
NFS/localio: Stop further I/O upon hitting an error
NFSv4.x: Directory delegations don't require any state recovery
NFSv4: Don't free slots prematurely if requesting a directory delegation
NFSv4: Fix nfs_clear_verifier_delegated() for delegated directories
NFS: Fix directory delegation verifier checks
pnfs/blocklayout: Fix memory leak in bl_parse_scsi()
pnfs/flexfiles: Fix memory leak in nfs4_ff_alloc_deviceid_node()
NFS: Fix a deadlock involving nfs_release_folio()
pNFS: Fix a deadlock when returning a delegation during open()
The pg_remaining calculation in ftrace_process_locs() assumes that
ENTRIES_PER_PAGE multiplied by 2^order equals the actual capacity of the
allocated page group. However, ENTRIES_PER_PAGE is PAGE_SIZE / ENTRY_SIZE
(integer division). When PAGE_SIZE is not a multiple of ENTRY_SIZE (e.g.
4096 / 24 = 170 with remainder 16), high-order allocations (like 256 pages)
have significantly more capacity than 256 * 170. This leads to pg_remaining
being underestimated, which in turn makes skip (derived from skipped -
pg_remaining) larger than expected, causing the WARN(skip != remaining)
to trigger.
Extra allocated pages for ftrace: 2 with 654 skipped
WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:7295 ftrace_process_locs+0x5bf/0x5e0
A similar problem in ftrace_allocate_records() can result in allocating
too many pages. This can trigger the second warning in
ftrace_process_locs().
Extra allocated pages for ftrace
WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:7276 ftrace_process_locs+0x548/0x580
Use the actual capacity of a page group to determine the number of pages
to allocate. Have ftrace_allocate_pages() return the number of allocated
pages to avoid having to calculate it. Use the actual page group capacity
when validating the number of unused pages due to skipped entries.
Drop the definition of ENTRIES_PER_PAGE since it is no longer used.
Cc: stable@vger.kernel.org
Fixes: 4a3efc6baff93 ("ftrace: Update the mcount_loc check of skipped entries")
Link: https://patch.msgid.link/20260113152243.3557219-1-linux@roeck-us.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Pull EFI fixes from Ard Biesheuvel:
- Wipe the INITRD config table upon consumption so it doesn't confuse
kexec
- Let APEI/GHES maintainers take responsibility for CPER processing
logic
- Fix wrong return value in CPER string helper routine
* tag 'efi-fixes-for-v6.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
efi/cper: Fix cper_bits_to_str buffer handling and return value
MAINTAINERS: add cper to APEI files
efi: Wipe INITRD config table from memory after consumption
If the pre-operation file size is read before locking the inode and
quiescing O_DIRECT writes, then nfs_truncate_last_folio() might end up
overwriting valid file data.
Fixes: b1817b18ff20 ("NFS: Protect against 'eof page pollution'")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Pull misc fixes from Andrew Morton:
- kerneldoc fixes from Bagas Sanjaya
- DAMON fixes from SeongJae
- mremap VMA-related fixes from Lorenzo
- various singletons - please see the changelogs for details
* tag 'mm-hotfixes-stable-2026-01-15-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (30 commits)
drivers/dax: add some missing kerneldoc comment fields for struct dev_dax
mm: numa,memblock: include <asm/numa.h> for 'numa_nodes_parsed'
mailmap: add entry for Daniel Thompson
tools/testing/selftests: fix gup_longterm for unknown fs
mm/page_alloc: prevent pcp corruption with SMP=n
iommu/sva: include mmu_notifier.h header
mm: kmsan: fix poisoning of high-order non-compound pages
tools/testing/selftests: add forked (un)/faulted VMA merge tests
mm/vma: enforce VMA fork limit on unfaulted,faulted mremap merge too
tools/testing/selftests: add tests for !tgt, src mremap() merges
mm/vma: fix anon_vma UAF on mremap() faulted, unfaulted merge
mm/zswap: fix error pointer free in zswap_cpu_comp_prepare()
mm/damon/sysfs-scheme: cleanup access_pattern subdirs on scheme dir setup failure
mm/damon/sysfs-scheme: cleanup quotas subdirs on scheme dir setup failure
mm/damon/sysfs: cleanup attrs subdirs on context dir setup failure
mm/damon/sysfs: cleanup intervals subdirs on attrs dir setup failure
mm/damon/core: remove call_control in inactive contexts
powerpc/watchdog: add support for hardlockup_sys_info sysctl
mips: fix HIGHMEM initialization
mm/hugetlb: ignore hugepage kernel args if hugepages are unsupported
...
The return value calculation was incorrect: `return len - buf_size;`
Initially `len = buf_size`, then `len` decreases with each operation.
This results in a negative return value on success.
Fix by returning `buf_size - len` which correctly calculates the actual
number of bytes written.
Fixes: a976d790f494 ("efi/cper: Add a new helper function to print bitmasks")
Signed-off-by: Morduan Zang <zhangdandan@uniontech.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
The function nfs_inode_evict_delegation() immediately and synchronously
returns a delegation when called. This means we can't call it from
nfs4_have_delegation(), since that function could be called under a
lock. Instead we should mark the delegation for return and let the state
manager handle it for us.
Fixes: b6d2a520f463 ("NFS: Add a module option to disable directory delegations")
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Pull crypto library fixes from Eric Biggers:
- A couple more fixes for the lib/crypto KUnit tests
- Fix missing MMU protection for the AES S-box
* tag 'libcrypto-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux:
lib/crypto: aes: Fix missing MMU protection for AES S-box
MAINTAINERS: add test vector generation scripts to "CRYPTO LIBRARY"
lib/crypto: tests: Fix syntax error for old python versions
lib/crypto: tests: polyval_kunit: Increase iterations for preparekey in IRQs
Pull networking fixes from Paolo Abeni:
"Including fixes from bluetooth, can and IPsec.
Current release - regressions:
- net: add net.core.qdisc_max_burst
- can: propagate CAN device capabilities via ml_priv
Previous releases - regressions:
- dst: fix races in rt6_uncached_list_del() and
rt_del_uncached_list()
- ipv6: fix use-after-free in inet6_addr_del().
- xfrm: fix inner mode lookup in tunnel mode GSO segmentation
- ip_tunnel: spread netdev_lockdep_set_classes()
- ip6_tunnel: use skb_vlan_inet_prepare() in __ip6_tnl_rcv()
- bluetooth: hci_sync: enable PA sync lost event
- eth: virtio-net:
- fix the deadlock when disabling rx NAPI
- fix misalignment bug in struct virtnet_info
Previous releases - always broken:
- ipv4: ip_gre: make ipgre_header() robust
- can: fix SSP_SRC in cases when bit-rate is higher than 1 MBit.
- eth:
- mlx5e: profile change fix
- octeon_ep_vf: fix free_irq dev_id mismatch in IRQ rollback
- macvlan: fix possible UAF in macvlan_forward_source()"
* tag 'net-6.19-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (37 commits)
virtio_net: Fix misalignment bug in struct virtnet_info
net: can: j1939: j1939_xtp_rx_rts_session_active(): deactivate session upon receiving the second rts
can: raw: instantly reject disabled CAN frames
can: propagate CAN device capabilities via ml_priv
Revert "can: raw: instantly reject unsupported CAN frames"
net/sched: sch_qfq: do not free existing class in qfq_change_class()
selftests: drv-net: fix RPS mask handling for high CPU numbers
selftests: drv-net: fix RPS mask handling in toeplitz test
ipv6: Fix use-after-free in inet6_addr_del().
dst: fix races in rt6_uncached_list_del() and rt_del_uncached_list()
net: hv_netvsc: reject RSS hash key programming without RX indirection table
tools: ynl: render event op docs correctly
net: add net.core.qdisc_max_burst
net: airoha: Fix typo in airoha_ppe_setup_tc_block_cb definition
net: phy: motorcomm: fix duplex setting error for phy leds
net: octeon_ep_vf: fix free_irq dev_id mismatch in IRQ rollback
net/mlx5e: Restore destroying state bit after profile cleanup
net/mlx5e: Pass netdev to mlx5e_destroy_netdev instead of priv
net/mlx5e: Don't store mlx5e_priv in mlx5e_dev devlink priv
net/mlx5e: Fix crash on profile change rollback failure
...
Add the missing @align and @memmap_on_memory fields to kerneldoc comment
header for struct dev_dax.
Also, some other fields were followed by '-' and others by ':'. Fix all
to be ':' for actual kerneldoc compliance.
Link: https://lkml.kernel.org/r/20260110191804.5739-1-john@groves.net
Fixes: 33cf94d71766 ("device-dax: make align a per-device property")
Fixes: 4eca0ef49af9 ("dax/kmem: allow kmem to add memory with memmap_on_memory")
Signed-off-by: John Groves <john@groves.net>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The CPER records are defined as part of UEFI specs, but its
primary way to report it is via APEI/GHES. As such, let's
place it under the same umbrella to make easier for patch
review.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
When resending requests, etc, the page base can quickly grow larger than
the page size.
Fixes: 091bdcfcece0 ("nfs/localio: refactor iocb and iov_iter_bvec initialization")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
Pull char/misc driver fixes from Greg KH:
"Here are some small char/misc driver fixes for some reported issues.
Included in here is:
- much reported rust_binder fix
- counter driver fixes
- new device ids for the mei driver
All of these have been in linux-next for a while with no reported
issues"
* tag 'char-misc-6.19-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
rust_binder: remove spin_lock() in rust_shrink_free_page()
mei: me: add nova lake point S DID
counter: 104-quad-8: Fix incorrect return value in IRQ handler
counter: interrupt-cnt: Drop IRQF_NO_THREAD flag