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
Clone this repository
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
Pull MIPS fixes from Thomas Bogendoerfer:
- Fix TLB uniquification for systems with TLB not initialised by
firmware
- Fix allocation in TLB uniquification
- Fix SiByte cache initialisation
- Check uart parameters from firmware on Loongson64 systems
- Fix clock id mismatch for Ralink SoCs
- Fix GCC version check for __mutli3 workaround
* tag 'mips-fixes_7.0_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
mips: mm: Allocate tlb_vpn array atomically
MIPS: mm: Rewrite TLB uniquification for the hidden bit feature
MIPS: mm: Suppress TLB uniquification on EHINV hardware
MIPS: Always record SEGBITS in cpu_data.vmbits
MIPS: Fix the GCC version check for `__multi3' workaround
MIPS: SiByte: Bring back cache initialisation
mips: ralink: update CPU clock index
MIPS: Loongson64: env: Check UARTs passed by LEFI cautiously
Pull char/misc/iio driver fixes from Greg KH:
"Here are a relativly large number of small char/misc/iio and other
driver fixes for 7.0-rc7. There's a bunch, but overall they are all
small fixes for issues that people have been having that I finally
caught up with getting merged due to delays on my end.
The "largest" change overall is just some documentation updates to the
security-bugs.rst file to hopefully tell the AI tools (and any users
that actually read the documentation), how to send us better security
bug reports as the quantity of reports these past few weeks has
increased dramatically due to tools getting better at "finding"
things.
Included in here are:
- lots of small IIO driver fixes for issues reported in 7.0-rc
- gpib driver fixes
- comedi driver fixes
- interconnect driver fix
- nvmem driver fixes
- mei driver fix
- counter driver fix
- binder rust driver fixes
- some other small misc driver fixes
All of these have been in linux-next this week with no reported issues"
* tag 'char-misc-7.0-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (63 commits)
Documentation: fix two typos in latest update to the security report howto
Documentation: clarify the mandatory and desirable info for security reports
Documentation: explain how to find maintainers addresses for security reports
Documentation: minor updates to the security contacts
.get_maintainer.ignore: add myself
nvmem: zynqmp_nvmem: Fix buffer size in DMA and memcpy
nvmem: imx: assign nvmem_cell_info::raw_len
misc: fastrpc: check qcom_scm_assign_mem() return in rpmsg_probe
misc: fastrpc: possible double-free of cctx->remote_heap
comedi: dt2815: add hardware detection to prevent crash
comedi: runflags cannot determine whether to reclaim chanlist
comedi: Reinit dev->spinlock between attachments to low-level drivers
comedi: me_daq: Fix potential overrun of firmware buffer
comedi: me4000: Fix potential overrun of firmware buffer
comedi: ni_atmio16d: Fix invalid clean-up after failed attach
gpib: fix use-after-free in IO ioctl handlers
gpib: lpvo_usb: fix memory leak on disconnect
gpib: Fix fluke driver s390 compile issue
lis3lv02d: Omit IRQF_ONESHOT if no threaded handler is provided
lis3lv02d: fix kernel-doc warnings
...
Found by DEBUG_ATOMIC_SLEEP:
BUG: sleeping function called from invalid context at /include/linux/sched/mm.h:306
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
no locks held by swapper/1/0.
irq event stamp: 0
hardirqs last enabled at (0): [<0000000000000000>] 0x0
hardirqs last disabled at (0): [<ffffffff801477fc>] copy_process+0x75c/0x1b68
softirqs last enabled at (0): [<ffffffff801477fc>] copy_process+0x75c/0x1b68
softirqs last disabled at (0): [<0000000000000000>] 0x0
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.6.119-d79e757675ec-fct #1
Stack : 800000000290bad8 0000000000000000 0000000000000008 800000000290bae8
800000000290bae8 800000000290bc78 0000000000000000 0000000000000000
ffffffff80c80000 0000000000000001 ffffffff80d8dee8 ffffffff810d09c0
784bb2a7ec10647d 0000000000000010 ffffffff80a6fd60 8000000001d8a9c0
0000000000000000 0000000000000000 ffffffff80d90000 0000000000000000
ffffffff80c9e0e8 0000000007ffffff 0000000000000cc0 0000000000000400
ffffffffffffffff 0000000000000001 0000000000000002 ffffffffc0149ed8
fffffffffffffffe 8000000002908000 800000000290bae0 ffffffff80a81b74
ffffffff80129fb0 0000000000000000 0000000000000000 0000000000000000
0000000000000000 0000000000000000 ffffffff80129fd0 0000000000000000
...
Call Trace:
[<ffffffff80129fd0>] show_stack+0x60/0x158
[<ffffffff80a7f894>] dump_stack_lvl+0x88/0xbc
[<ffffffff8018d3c8>] __might_resched+0x268/0x288
[<ffffffff803648b0>] __kmem_cache_alloc_node+0x2e0/0x330
[<ffffffff80302788>] __kmalloc+0x58/0xd0
[<ffffffff80a81b74>] r4k_tlb_uniquify+0x7c/0x428
[<ffffffff80143e8c>] tlb_init+0x7c/0x110
[<ffffffff8012bdb4>] per_cpu_trap_init+0x16c/0x1d0
[<ffffffff80133258>] start_secondary+0x28/0x128
Fixes: 231ac951faba ("MIPS: mm: kmalloc tlb_vpn array to avoid stack overflow")
Signed-off-by: Stefan Wiehler <stefan.wiehler@nokia.com>
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Pull tty fixes from Greg KH:
"Here are two small tty vt fixes for 7.0-rc7 to resolve some reported
issues with the resize ability of the alt screen buffer. Both of these
have been in linux-next all week with no reported issues"
* tag 'tty-7.0-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
vt: resize saved unicode buffer on alt screen exit after resize
vt: discard stale unicode buffer on alt screen exit after resize
In previous patch "Documentation: clarify the mandatory and desirable
info for security reports" I left two typos that I didn't detect in local
checks. One is "get_maintainers.pl" (no 's' in the script name), and the
other one is a missing closing quote after "Reported-by", which didn't
have effect here but I don't know if it can break rendering elsewhere
(e.g. on the public HTML page). Better fix it before it gets merged.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260404082033.5160-1-w@1wt.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Before the introduction of the EHINV feature, which lets software mark
TLB entries invalid, certain older implementations of the MIPS ISA were
equipped with an analogous bit, as a vendor extension, which however is
hidden from software and only ever set at reset, and then any software
write clears it, making the intended TLB entry valid.
This feature makes it unsafe to read a TLB entry with TLBR, modify the
page mask, and write the entry back with TLBWI, because this operation
will implicitly clear the hidden bit and this may create a duplicate
entry, as with the presence of the hidden bit there is no guarantee all
the entries across the TLB are unique each.
Usually the firmware has already uniquified TLB entries before handing
control over, in which case we only need to guarantee at bootstrap no
clash will happen with the VPN2 values chosen in local_flush_tlb_all().
However with systems such as Mikrotik RB532 we get handed the TLB as at
reset, with the hidden bit set across the entries and possibly duplicate
entries present. This then causes a machine check exception when page
sizes are reset in r4k_tlb_uniquify() and prevents the system from
booting.
Rewrite the algorithm used in r4k_tlb_uniquify() then such as to avoid
the reuse of ASID/VPN values across the TLB. Get rid of global entries
first as they may be blocking the entire address space, e.g. 16 256MiB
pages will exhaust the whole address space of a 32-bit CPU and a single
big page can exhaust the 32-bit compatibility space on a 64-bit CPU.
Details of the algorithm chosen are given across the code itself.
Fixes: 9f048fa48740 ("MIPS: mm: Prevent a TLB shutdown on initial uniquification")
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Cc: stable@vger.kernel.org # v6.18+
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Pull USB/Thunderbolt fixes from Greg KH:
"Here are a bunch of USB and Thunderbolt fixes (most all are USB) for
7.0-rc7. More than I normally like this late in the release cycle,
partly due to my recent travels, and partly due to people banging away
on the USB gadget interfaces and apis more than normal (big shoutout
to Android for getting the vendors to actually work upstream on this,
that's a huge win overall for everyone here)
Included in here are:
- Small thunderbolt fix
- new USB serial driver ids added
- typec driver fixes
- gadget driver fixes for some disconnect issues
- other usb gadget driver fixes for reported problems with binding
and unbinding devices as happens when a gadget device connects /
disconnects from a system it is plugged into (or it switches device
mode at a user's request, these things are complex little
beasts...)
- usb offload fixes (where USB audio tunnels through the controller
while the main CPU is asleep) for when EMP spikes hit the system
causing disconnects to happen (as often happens with static
electricity in the winter months). This has been much reported by
at least one vendor, and resolves the issues they have been seeing
with this codepath. Can't wait for the "formal methods are the
answer!" people to try to model that one properly...
- Other small usb driver fixes for issues reported.
All of these have been in linux-next this week, and before, with no
reported issues, and I've personally been stressing these harder than
normal on my systems here with no problems"
* tag 'usb-7.0-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (39 commits)
usb: gadget: f_hid: move list and spinlock inits from bind to alloc
usb: host: xhci-sideband: delegate offload_usage tracking to class drivers
usb: core: use dedicated spinlock for offload state
usb: cdns3: gadget: fix state inconsistency on gadget init failure
usb: dwc3: imx8mp: fix memory leak on probe failure path
usb: gadget: f_uac1_legacy: validate control request size
usb: ulpi: fix double free in ulpi_register_interface() error path
usb: misc: usbio: Fix URB memory leak on submit failure
USB: core: add NO_LPM quirk for Razer Kiyo Pro webcam
usb: cdns3: gadget: fix NULL pointer dereference in ep_queue
usb: core: phy: avoid double use of 'usb3-phy'
USB: serial: option: add MeiG Smart SRM825WN
usb: gadget: f_rndis: Fix net_device lifecycle with device_move
usb: gadget: f_subset: Fix net_device lifecycle with device_move
usb: gadget: f_eem: Fix net_device lifecycle with device_move
usb: gadget: f_ecm: Fix net_device lifecycle with device_move
usb: gadget: u_ncm: Add kernel-doc comments for struct f_ncm_opts
usb: gadget: f_rndis: Protect RNDIS options with mutex
usb: gadget: f_subset: Fix unbalanced refcnt in geth_free
dt-bindings: connector: add pd-disable dependency
...
Instead of discarding the saved unicode buffer when the console was
resized while in the alternate screen, resize it to the current
dimensions using vc_uniscr_copy_area() to preserve its content. This
properly restores the unicode screen on alt screen exit rather than
lazily rebuilding it from a lossy reverse glyph translation.
On allocation failure the stale buffer is freed and vc_uni_lines is
set to NULL so it gets lazily rebuilt via vc_uniscr_check() when next
needed.
Fixes: 40014493cece ("vt: discard stale unicode buffer on alt screen exit after resize")
Cc: stable <stable@kernel.org>
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Link: https://patch.msgid.link/3nsr334n-079q-125n-7807-n4nq818758ns@syhkavp.arg
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
A significant part of the effort of the security team consists in begging
reporters for patch proposals, or asking them to provide them in regular
format, and most of the time they're willing to provide this, they just
didn't know that it would help. So let's add a section detailing the
required and desirable contents in a security report to help reporters
write more actionable reports which do not require round trips.
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260403062018.31080-4-w@1wt.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Hardware that supports the EHINV feature, mandatory for R6 ISA and FTLB
implementation, lets software mark TLB entries invalid, which eliminates
the need to ensure no duplicate matching entries are ever created. This
feature is already used by local_flush_tlb_all(), via the UNIQUE_ENTRYHI
macro, making the preceding call to r4k_tlb_uniquify() superfluous.
The next change will also modify uniquification code such that it'll
become incompatible with the FTLB and MMID features, as well as MIPSr6
CPUs that do not implement 4KiB pages.
Therefore prevent r4k_tlb_uniquify() from being used on EHINV hardware,
as denoted by `cpu_has_tlbinv'.
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Pull input fixes from Dmitry Torokhov:
- new IDs for BETOP BTP-KP50B/C and Razer Wolverine V3 Pro added to
xpad controller driver
- another quirk for new TUXEDO InfinityBook added to i8042
- a small fixup for Synaptics RMI4 driver to properly unlock mutex when
encountering an error in F54
- an update to bcm5974 touch controller driver to reliably switch into
wellspring mode
* tag 'input-for-v7.0-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
Input: xpad - add support for BETOP BTP-KP50B/C controller's wireless mode
Input: xpad - add support for Razer Wolverine V3 Pro
Input: synaptics-rmi4 - fix a locking bug in an error path
Input: i8042 - add TUXEDO InfinityBook Max 16 Gen10 AMD to i8042 quirk table
Input: bcm5974 - recover from failed mode switch
Johan writes:
USB serial device ids for 7.0-rc7
Here are some new modem and io_edgeport device ids.
All have been in linux-next with no reported issues.
* tag 'usb-serial-7.0-rc7' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial:
USB: serial: option: add MeiG Smart SRM825WN
USB: serial: io_edgeport: add support for Blackbox IC135A
USB: serial: option: add support for Rolling Wireless RW135R-GL
When enter_alt_screen() saves vc_uni_lines into vc_saved_uni_lines and
sets vc_uni_lines to NULL, a subsequent console resize via vc_do_resize()
skips reallocating the unicode buffer because vc_uni_lines is NULL.
However, vc_saved_uni_lines still points to the old buffer allocated for
the original dimensions.
When leave_alt_screen() later restores vc_saved_uni_lines, the buffer
dimensions no longer match vc_rows/vc_cols. Any operation that iterates
over the unicode buffer using the current dimensions (e.g. csi_J clearing
the screen) will access memory out of bounds, causing a kernel oops:
BUG: unable to handle page fault for address: 0x0000002000000020
RIP: 0010:csi_J+0x133/0x2d0
The faulting address 0x0000002000000020 is two adjacent u32 space
characters (0x20) interpreted as a pointer, read from the row data area
past the end of the 25-entry pointer array in a buffer allocated for
80x25 but accessed with 240x67 dimensions.
Fix this by checking whether the console dimensions changed while in the
alternate screen. If they did, free the stale saved buffer instead of
restoring it. The unicode screen will be lazily rebuilt via
vc_uniscr_check() when next needed.
Fixes: 5eb608319bb5 ("vt: save/restore unicode screen buffer for alternate screen")
Cc: stable <stable@kernel.org>
Tested-by: Liav Mordouch <liavmordouch@gmail.com>
Signed-off-by: Liav Mordouch <liavmordouch@gmail.com>
Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
Link: https://patch.msgid.link/20260327170204.29706-1-liavmordouch@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
These days, 80% of the work done by the security team consists in
locating the affected subsystem in a report, running get_maintainers on
it, forwarding the report to these persons and responding to the reporter
with them in Cc. This is a huge and unneeded overhead that we must try to
lower for a better overall efficiency. This patch adds a complete section
explaining how to figure the list of recipients to send the report to.
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260403062018.31080-3-w@1wt.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
With a 32-bit kernel running on 64-bit MIPS hardware the hardcoded value
of `cpu_vmbits' only records the size of compatibility useg and does not
reflect the size of native xuseg or the complete range of values allowed
in the VPN2 field of TLB entries.
An upcoming change will need the actual VPN2 value range permitted even
in 32-bit kernel configurations, so always include the `vmbits' member
in `struct cpuinfo_mips' and probe for SEGBITS when running on 64-bit
hardware and resorting to the currently hardcoded value of 31 on 32-bit
processors. No functional change for users of `cpu_vmbits'.
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Pull powerpc fix from Madhavan Srinivasan:
- fix iommu incorrectly bypassing DMA APIs
Thanks to Dan Horak, Gaurav Batra, and Ritesh Harjani (IBM).
* tag 'powerpc-7.0-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/powernv/iommu: iommu incorrectly bypass DMA APIs