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. 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Pull smb server fixes from Steve French:
- Fix shutdown (stop sessions)
- Fix readdir unsupported info level
* tag 'v7.1-rc2-ksmbd-server-fixes' of git://git.samba.org/ksmbd:
ksmbd: rewrite stop_sessions() with restartable iteration
smb: server: handle readdir_info_level_struct_sz() error
Pull block fixes from Jens Axboe:
- MD pull request via Yu:
- Fix a raid5 UAF on IO across the reshape position
- Avoid failing RAID1/RAID10 devices for invalid IO errors
- Fix RAID10 divide-by-zero when far_copies is zero
- Restore bitmap grow through sysfs
- Use mddev_is_dm() instead of open-coding gendisk checks
- Use ATTRIBUTE_GROUPS() for md default sysfs attributes
- Replace open-coded wait loops with wait_event helpers
- NVMe pull request via Keith:
- Target data transfer size configuation (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)
- Properly propagate CDROM read-only state to the block layer
* tag 'block-7.1-20260430' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux: (35 commits)
md: use ATTRIBUTE_GROUPS() for md default sysfs attributes
md: use mddev_is_dm() instead of open-coding gendisk checks
md/raid1: replace wait loop with wait_event_idle() in raid1_write_request()
md/md-bitmap: add a none backend for bitmap grow
md/md-bitmap: split bitmap sysfs groups
md: factor bitmap creation away from sysfs handling
md: use mddev_lock_nointr() in mddev_suspend_and_lock_nointr()
md: replace wait loop with wait_event() in md_handle_request()
md/raid10: fix divide-by-zero in setup_geo() with zero far_copies
md/raid1,raid10: don't fail devices for invalid IO errors
MAINTAINERS: Add Xiao Ni as md/raid reviewer
md/raid5: Fix UAF on IO across the reshape position
cdrom, scsi: sr: propagate read-only status to block layer via set_disk_ro()
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
...
stop_sessions() walks conn_list with hash_for_each() and, for every
entry, drops conn_list_lock across the transport ->shutdown() call
before re-acquiring the read lock to continue the loop. The hash
walk relies on cross-iteration state (the current bucket and the
hlist position), which is not preserved across unlock/relock: if
another thread performs a list mutation during the unlocked window,
the ongoing iteration becomes unreliable and can re-visit
connections that have already been handled or skip connections that
have not. The outer `if (!hash_empty(conn_list)) goto again;` retry
masks the symptom in the common case but does not address the
unsafe iteration itself.
Reframe the loop so it never relies on iterator state across
unlock/relock. Under conn_list_lock held for read, pick the first
connection whose ->shutdown() has not yet been issued by this path,
pin it by taking an extra reference, record that fact on the
connection and mark it EXITING while still inside the locked walk,
then drop the lock. Then call ->shutdown() outside the lock, drop
the pin (freeing the connection if the handler already released its
reference), and restart from the top.
Use a new per-connection flag, conn->stop_called, as the "shutdown
issued from stop_sessions()" marker rather than reusing the status
state. ksmbd_conn_set_exiting() is also invoked by
ksmbd_sessions_deregister() on sibling channels of a multichannel
session without issuing a transport shutdown, so treating
KSMBD_SESS_EXITING as "already handled here" would skip connections
that still need shutdown() to wake their handler out of recv(),
leaving the outer retry waiting indefinitely for the hash to drain.
stop_sessions() is serialised by init_lock in
ksmbd_conn_transport_destroy(), so writing stop_called under the
read lock has no other writer.
Set EXITING inside the locked walk so the selection, the stop_called
marker, and the status transition all happen together, and guard
against regressing a connection that has already advanced to
KSMBD_SESS_RELEASING on its own (for example, if the handler exited
its receive loop for an unrelated reason between teardown steps).
When the pin drop is the last put, release the transport and pair
ida_destroy(&target->async_ida) with the ida_init() done in
ksmbd_conn_alloc(), so stop_sessions() retiring a connection on its
own does not leak the xarray backing of the embedded async_ida.
The outer retry with msleep() is kept to wait for handler threads to
reach ksmbd_conn_free() and drain the hash.
Observed with an instrumented build that logs one line per visit and
widens the unlocked window before ->shutdown() by 200 ms, under
five concurrent cifs mounts (nosharesock, one connection each):
* Current code: the same connection address is revisited many
times during a single stop_sessions() call and ->shutdown() is
invoked well beyond the number of live connections before the
hash finally drains.
* Rewritten code: each live connection produces exactly one
->shutdown() call; the function returns as soon as the hash is
empty.
Functional teardown via `ksmbd.control --shutdown` with the same
five mounts completes cleanly on the rewritten path.
Performance is observably unchanged. Tearing down N concurrent
nosharesock cifs connections with `ksmbd.control --shutdown` +
`rmmod ksmbd` takes essentially the same wall time before and after
the rewrite:
N before after
10 4.93s 5.34s
30 7.34s 7.03s
50 7.31s 7.01s (3-run avg: 7.04s vs 7.25s)
100 6.98s 6.78s
200 6.77s 6.89s
and the number of ->shutdown() calls equals the number of live
connections on both paths when the race is not widened. The
teardown is dominated by the msleep(100)-based outer retry waiting
for handler threads to run ksmbd_conn_free(), not by the iteration
itself; the restartable loop's worst-case O(N^2) visit cost is in
the microseconds even at N=200 and sits far below the msleep(100)
granularity.
Applied alone on top of ksmbd-for-next-next, this patch does not
introduce a new leak site. Under the same reproducer (10x
concurrent-holders + ss -K + ksmbd.control --shutdown + rmmod), the
tree still shows the pre-existing per-connection transport leak
count that arises when the last refcount drop lands in one of
ksmbd_conn_r_count_dec(), __free_opinfo() or session_fd_check() -
all of which end with a bare kfree() today. kmemleak backtraces
for the unreferenced objects point into the TCP accept path
(sk_clone -> inet_csk_clone_lock, sock_alloc_inode) and none
involve stop_sessions(). Plugging those bare-kfree sites is the
responsibility of the follow-up patch.
Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Signed-off-by: DaeMyung Kang <charsyam@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Pull io_uring fixes from Jens Axboe:
- Remove dead struct io_buffer_list member
- Fix for incrementally consumed buffers with recvmsg multishot, which
requires a minimum value left in a buffer for any receive for the
headers. If there's still a bit of buffer left but it's smaller than
that value, then userspace will see a spurious -EFAULT returned in
the CQE
- Locking fix for the DEFER_TASKRUN retry list, which otherwise could
race with fallback cancelations. If the task is exiting with
task_work left in both the normal and retry list AND the exit cleanup
races with the task running task work, then entries could either be
doubly completed or lost
- Cap NAPI busy poll timeout to something sane, to avoid syzbot running
into excessive polling and triggering warnings around that
* tag 'io_uring-7.1-20260430' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux:
io_uring/tw: serialize ctx->retry_llist with ->uring_lock
io_uring/napi: cap busy_poll_to 10 msec
io_uring/kbuf: support min length left for incremental buffers
io_uring/kbuf: kill dead struct io_buffer_list 'nr_entries' member
Pull MD fixes from Yu Kuai:
"Bug Fixes:
- Fix a raid5 UAF on IO across the reshape position.
- Avoid failing RAID1/RAID10 devices for invalid IO errors.
- Fix RAID10 divide-by-zero when far_copies is zero.
- Restore bitmap grow through sysfs.
Cleanups:
- Use mddev_is_dm() instead of open-coding gendisk checks.
- Use ATTRIBUTE_GROUPS() for md default sysfs attributes.
- Replace open-coded wait loops with wait_event helpers."
* tag 'md-7.1-20260428' of https://git.kernel.org/pub/scm/linux/kernel/git/mdraid/linux:
md: use ATTRIBUTE_GROUPS() for md default sysfs attributes
md: use mddev_is_dm() instead of open-coding gendisk checks
md/raid1: replace wait loop with wait_event_idle() in raid1_write_request()
md/md-bitmap: add a none backend for bitmap grow
md/md-bitmap: split bitmap sysfs groups
md: factor bitmap creation away from sysfs handling
md: use mddev_lock_nointr() in mddev_suspend_and_lock_nointr()
md: replace wait loop with wait_event() in md_handle_request()
md/raid10: fix divide-by-zero in setup_geo() with zero far_copies
md/raid1,raid10: don't fail devices for invalid IO errors
MAINTAINERS: Add Xiao Ni as md/raid reviewer
md/raid5: Fix UAF on IO across the reshape position
early exit in smb2_populate_readdir_entry() if the requested info_level
is unknown.
Signed-off-by: Marios Makassikis <mmakassikis@freebox.fr>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Pull spi fixes from Mark Brown:
"There are a couple of nasty issues fixed here in the axiado and
rockchip drivers. We've also got more of the fixes from Johan here,
this time for the two Cadence drivers, plus a couple of other similar
fixes from John and Felix"
* tag 'spi-fix-v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi:
spi: amlogic-spisg: initialize completion before requesting IRQ
spi: axiado: replace usleep_range() with udelay() in IRQ path
spi: cadence-quadspi: fix runtime pm and clock imbalance on unbind
spi: cadence-quadspi: fix unclocked access on unbind
spi: cadence-quadspi: fix clock imbalance on probe failure
spi: cadence-quadspi: fix runtime pm disable imbalance on probe failure
spi: cadence: fix clock imbalance on probe failure
spi: cadence: fix unclocked access on unbind
spi: rockchip: Drop unused and broken CR0 macros
spi: rockchip: Read ISR, not IMR, to detect cs-inactive IRQ
spi: rzv2h-rspi: Fix silent failure in clock setup error path
The DEFER_TASKRUN local task work paths all run under ctx->uring_lock,
which serializes them with each other and with the rest of the ring's
hot paths. io_move_task_work_from_local() is the exception - it's called
from io_ring_exit_work() on a kworker without holding the lock and from
the iopoll cancelation side right after dropping it.
->work_llist is fine with this, as it's only ever updated via the
expected paths. But the ->retry_llist is updated while runing, and hence
it could potentially race between normal task_work running and the
task-has-exited shutdown path.
Simply grab ->uring_lock while moving the local work to the fallback
list for exit purposes, which nicely serializes it across both the
normal additions and the exit prune path.
Cc: stable@vger.kernel.org
Fixes: f46b9cdb22f7 ("io_uring: limit local tw done")
Reported-by: Robert Femmer <robert.femmer@x41-dsec.de>
Reported-by: Christian Reitter <invd@inhq.net>
Reported-by: Michael Rodler <michael.rodler@x41-dsec.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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>
Replace the md_default_group and md_attr_groups with
ATTRIBUTE_GROUPS().
Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
Link: https://lore.kernel.org/linux-raid/20260423101303.48196-4-abd.masalkhi@gmail.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Pull regulator fix from Mark Brown:
"A fix from Arnd re-adding a dependency on gpiolib which was implicitly
pulled in via an OF specific route which got removed as part of a
cleanup"
* tag 'regulator-fix-v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator:
regulator: rpi-panel-attiny: add back GPIOLIB dependency
Several fixes from Johan for issues with unbind and error handling in
probe.
Currently there's no cap on the maximum amount of time that napi is
allowed to poll if no events are found, which can lead to kernel
complaints on a task being stuck as there's no conditional rescheduling
done within that loop.
Just cap it to 10 msec in total, that's already way above any kind of
sane value that will reap any benefits, yet low enough that it's
nowhere near being able to trigger preemption complaints.
Fixes: 8d0c12a80cde ("io-uring: add napi busy poll support")
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
...
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>
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