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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Replace direct checks on mddev->gendisk with mddev_is_dm() in
md_handle_request() and md_run().
Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
Link: https://lore.kernel.org/linux-raid/20260423101303.48196-3-abd.masalkhi@gmail.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
The wait loop is equivalent to wait_event_idle(); use it to improve
readability.
Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
Link: https://lore.kernel.org/linux-raid/20260423101303.48196-2-abd.masalkhi@gmail.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Add a real none bitmap backend that exposes the common bitmap sysfs
group and use it to keep bitmap/location available when an array has no
bitmap.
Then switch the bitmap location sysfs path to move only between none
and the classic bitmap backend, using the no-sysfs bitmap helpers while
merging or unmerging the internal bitmap sysfs group.
This restores mdadm --grow bitmap addition through bitmap/location.
Fixes: fb8cc3b0d9db ("md/md-bitmap: delay registration of bitmap_ops until creating bitmap")
Reviewed-by: Su Yue <glass.su@suse.com>
Link: https://lore.kernel.org/r/20260425024615.1696892-4-yukuai@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Split the classic bitmap sysfs files into a common bitmap group with
the location attribute and a separate internal bitmap group for the
remaining files.
At the same time, convert bitmap operations from a single sysfs group
to a sysfs group array so backends can share part of their sysfs
layout while adding backend-specific attributes separately.
Switch the bitmap sysfs helpers to use sysfs_update_groups() for the
add and update path, and remove groups in reverse order so shared named
groups are unmerged before the last group removes the directory.
Also make bitmap operation lookup depend only on the currently selected
bitmap id matching the installed backend. This prepares the lookup path
for a later registered none backend.
Reviewed-by: Su Yue <glass.su@suse.com>
Link: https://lore.kernel.org/r/20260425024615.1696892-3-yukuai@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Factor bitmap creation and destruction into helpers that do not touch
bitmap sysfs registration.
This prepares the bitmap sysfs rework so callers such as the sysfs
bitmap location path can create or destroy a bitmap backend without
coupling that to sysfs group lifetime management.
Reviewed-by: Su Yue <glass.su@suse.com>
Link: https://lore.kernel.org/r/20260425024615.1696892-2-yukuai@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
This keeps mddev locking consistent and ensures that any future changes
to locking behavior are done through the wrapper.
Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
Link: https://lore.kernel.org/r/20260415140319.376578-3-abd.masalkhi@gmail.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
The wait loop is equivalent to wait_event() and can be simplified by
usaing it for improving readability.
Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
Link: https://lore.kernel.org/r/20260415140319.376578-2-abd.masalkhi@gmail.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
setup_geo() extracts near_copies (nc) and far_copies (fc) from the
user-provided layout parameter without checking for zero. When fc=0
with the "improved" far set layout selected, 'geo->far_set_size =
disks / fc' triggers a divide-by-zero.
Validate nc and fc immediately after extraction, returning -1 if
either is zero.
Fixes: 475901aff158 ("MD RAID10: Improve redundancy for 'far' and 'offset' algorithms (part 1)")
Cc: stable@vger.kernel.org
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Link: https://lore.kernel.org/linux-raid/SYBPR01MB7881A5E2556806CC1D318582AF232@SYBPR01MB7881.ausprd01.prod.outlook.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
BLK_STS_INVAL indicates the IO request itself was invalid, not that the
device has failed. When raid1 treats this as a device error, it retries
on alternate mirrors which fail the same way, eventually exceeding the
read error threshold and removing the device from the array.
This happens when stacking configurations bypass bio_split_to_limits()
in the IO path: dm-raid calls md_handle_request() directly without going
through md_submit_bio(), skipping the alignment validation that would
otherwise reject invalid bios early. The invalid bio reaches the
lower block layers, which fail the bio with BLK_STS_INVAL, and raid1
wrongly interprets this as a device failure.
Add BLK_STS_INVAL to raid1_should_handle_error() so that invalid IO
errors are propagated back to the caller rather than triggering device
removal. This is consistent with the previous kernel behavior when
alignment checks were done earlier in the direct-io path.
Fixes: 5ff3f74e145adc7 ("block: simplify direct io validity check")
Reported-by: Tomáš Trnka <trnka@scm.com>
Closes: https://lore.kernel.org/linux-block/2982107.4sosBPzcNG@electra/
Signed-off-by: Keith Busch <kbusch@kernel.org>
Tested-by: Tomáš Trnka <trnka@scm.com>
Link: https://lore.kernel.org/r/20260416140345.3872265-1-kbusch@meta.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
I've been actively involved in the md subsystem, contributing bug
fixes, performance improvements, and participating in code reviews.
I will help improve patch review coverage and response time.
Signed-off-by: Xiao Ni <xiao@kernel.org>
Link: https://lore.kernel.org/r/20260414022956.48271-1-xiaoraid25@gmail.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
If make_stripe_request() returns STRIPE_WAIT_RESHAPE,
raid5_make_request() will free the cloned bio. But raid5_make_request()
can call make_stripe_request() multiple times, writing to the various
stripes. If that bio got added to the toread or towrite lists of a
stripe disk in an earlier call to make_stripe_request(), then it's not
safe to just free the bio if a later part of it is found to cross the
reshape position. Doing so can lead to a UAF error, when bio_endio()
is called on the bio for the earlier stripes.
Instead, raid5_make_request() needs to wait until all parts of the bio
have called bio_endio(). To do this, bios that cross the reshape
position while the reshape can't make progress are flagged as needing to
wait for all parts to complete. When raid5_make_request() has a bio that
failed make_stripe_request() with STRIPE_WAIT_RESHAPE, it sets
bi->bi_private to a completion struct and waits for completion after
ending the bio. When the bio_endio() is called for the last time on a
clone bio with bi->bi_private set, it wakes up the waiter. This
guarantees that raid5_make_request() doesn't return until the cloned bio
needing a retry for io across the reshape boundary is safely cleaned up.
There is a simple reproducer available at [1]. Compile the kernel with
KASAN for more useful reporting when the error is triggered (this is not
necessary to see the bug).
[1] https://gist.github.com/bmarzins/e48598824305cf2171289e47d7241fa5
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Link: https://lore.kernel.org/r/20260408043548.1695157-1-bmarzins@redhat.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
The cdrom core never calls set_disk_ro() for a registered device, so
BLKROGET on a CD-ROM device always returns 0 (writable), even when the
drive has no write capabilities and writes will inevitably fail. This
causes problems for userspace that relies on BLKROGET to determine
whether a block device is read-only. For example, systemd's loop device
setup uses BLKROGET to decide whether to create a loop device with
LO_FLAGS_READ_ONLY. Without the read-only flag, writes pass through the
loop device to the CD-ROM and fail with I/O errors. systemd-fsck
similarly checks BLKROGET to decide whether to run fsck in no-repair
mode (-n).
The write-capability bits in cdi->mask come from two different sources:
CDC_DVD_RAM and CDC_CD_RW are populated by the driver from the MODE
SENSE capabilities page (page 0x2A) before register_cdrom() is called,
while CDC_MRW_W and CDC_RAM require the MMC GET CONFIGURATION command
and were only probed by cdrom_open_write() at device open time. This
meant that any attempt to compute the writable state from the full
mask at probe time was incorrect, because the GET CONFIGURATION bits
were still unset (and cdi->mask is initialized such that capabilities
are assumed present).
Fix this by factoring the GET CONFIGURATION probing out of
cdrom_open_write() into a new exported helper,
cdrom_probe_write_features(), and having sr call it from sr_probe()
right after get_capabilities() has populated the MODE SENSE bits.
register_cdrom() then calls set_disk_ro() based on the full
write-capability mask (CDC_DVD_RAM | CDC_MRW_W | CDC_RAM | CDC_CD_RW)
so the block layer reflects the drive's actual write support. The
feature queries used (CDF_MRW and CDF_RWRT via GET CONFIGURATION with
RT=00) report drive-level capabilities that are persistent across
media, so a single probe before register_cdrom() is sufficient and the
redundant probe at open time is dropped.
With set_disk_ro() now accurate, the long-vestigial cd->writeable flag
in sr can go: get_capabilities() used to set cd->writeable based on
the same four mask bits, but because CDC_MRW_W and CDC_RAM default to
"capability present" in cdi->mask and aren't touched by MODE SENSE,
the condition that gated cd->writeable was always true, making it
unconditionally 1. Replace the corresponding gate in sr_init_command()
with get_disk_ro(cd->disk), which turns a previously no-op check into
a real one and also catches kernel-internal bio writers that bypass
blkdev_write_iter()'s bdev_read_only() check.
The sd driver (SCSI disks) does not have this problem because it
checks the MODE SENSE Write Protect bit and calls set_disk_ro()
accordingly. The sr driver cannot use the same approach because the
MMC specification does not define the WP bit in the MODE SENSE
device-specific parameter byte for CD-ROM devices.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Daan De Meyer <daan@amutable.com>
Reviewed-by: Phillip Potter <phil@philpotter.co.uk>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://patch.msgid.link/20260427210139.1400-2-phil@philpotter.co.uk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Pull NVMe fixes from Keith:
"- Target data transfer size confiruation (Aurelien)
- Enable P2P for RDMA (Shivaji Kant)
- TCP target updates (Maurizio, Alistair, Chaitanya, Shivam Kumar)
- TCP host updates (Alistair, Chaitanya)
- Authentication updates (Alistair, Daniel, Chris Leech)
- Multipath fixes (John Garry)
- New quirks (Alan Cui, Tao Jiang)
- Apple driver fix (Fedor Pchelkin)
- PCI admin doorbell update fix (Keith)"
* tag 'nvme-7.1-2026-04-24' of git://git.infradead.org/nvme: (22 commits)
nvme-auth: Hash DH shared secret to create session key
nvme-pci: fix missed admin queue sq doorbell write
nvme-auth: Include SC_C in RVAL controller hash
nvme-tcp: teardown circular locking fixes
nvmet-tcp: Don't clear tls_key when freeing sq
Revert "nvmet-tcp: Don't free SQ on authentication success"
nvme: skip trace completion for host path errors
nvme-pci: add quirk for Memblaze Pblaze5 (0x1c5f:0x0555)
nvme-multipath: put module reference when delayed removal work is canceled
nvme: expose TLS mode
nvme-apple: drop invalid put of admin queue reference count
nvme-core: fix parameter name in comment
nvmet: avoid recursive nvmet-wq flush in nvmet_ctrl_free
nvme-multipath: drop head pointer check in nvme_mpath_clear_current_path()
nvme: add quirk NVME_QUIRK_IGNORE_DEV_SUBNQN for 144d:a808 (Samsung PM981/983/970 EVO Plus )
nvmet-tcp: fix race between ICReq handling and queue teardown
nvmet-tcp: remove redundant calls to nvmet_tcp_fatal_error()
nvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers
nvme: enable PCI P2PDMA support for RDMA transport
nvmet: introduce new mdts configuration entry
...
The NVMe Base Specification 8.3.5.5.9 states that the session key Ks
shall be computed from the ephemeral DH key by applying the hash
function selected by the HashID parameter.
The current implementation stores the raw DH shared secret as the
session key without hashing it. This causes redundant hash operations:
1. Augmented challenge computation (section 8.3.5.5.4) requires
Ca = HMAC(H(g^xy mod p), C). The code compensates by hashing the
unhashed session key in nvme_auth_augmented_challenge() to produce
the correct result.
2. PSK generation (section 8.3.5.5.9) requires PSK = HMAC(Ks, C1 || C2)
where Ks should already be H(g^xy mod p). As the DH shared secret
is always larger than the HMAC block size, HMAC internally hashes
it before use, accidentally producing the correct result.
When using secure channel concatenation with bidirectional
authentication, this results in hashing the DH value three times: twice
for augmented challenge calculations and once during PSK generation.
Fix this by:
- Modifying nvme_auth_gen_shared_secret() to hash the DH shared secret
once after computation: Ks = H(g^xy mod p)
- Removing the hash operation from nvme_auth_augmented_challenge()
as the session key is now already hashed
- Updating session key buffer size from DH key size to hash output size
- Adding specification references in comments
This avoid storing the raw DH shared secret and reduces the number of
hash operations from three to one when using secure channel
concatenation.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Pull clk fix from Stephen Boyd:
"One more fix for the merge window to avoid a boot hang on
Raspberry Pi 3B by marking the VEC clk critical so that it
doesn't get turned off and hang the bus"
* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
clk: bcm: rpi: Mark VEC clock as CLK_IGNORE_UNUSED
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