Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
Clone this repository
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
Pull Kbuild fixes from Nathan Chancellor:
- Formally adopt Kconfig in MAINTAINERS
- Fix install-extmod-build for more O= paths
- Align end of .modinfo to fix Authenticode calculation in EDK2
- Restore dynamic check for '-fsanitize=kernel-memory' in
CONFIG_HAVE_KMSAN_COMPILER to ensure backend target has support
for it
- Initialize locale in menuconfig and nconfig to fix UTF-8 terminals
that may not support VT100 ACS by default like PuTTY
* tag 'kbuild-fixes-6.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux:
kconfig/nconf: Initialize the default locale at startup
kconfig/mconf: Initialize the default locale at startup
KMSAN: Restore dynamic check for '-fsanitize=kernel-memory'
kbuild: align modinfo section for Secureboot Authenticode EDK2 compat
kbuild: install-extmod-build: Fix when given dir outside the build dir
MAINTAINERS: Update Kconfig section
Pull bpf fixes from Alexei Starovoitov:
- Mark migrate_disable/enable() as always_inline to avoid issues with
partial inlining (Yonghong Song)
- Fix powerpc stack register definition in libbpf bpf_tracing.h (Andrii
Nakryiko)
- Reject negative head_room in __bpf_skb_change_head (Daniel Borkmann)
- Conditionally include dynptr copy kfuncs (Malin Jonsson)
- Sync pending IRQ work before freeing BPF ring buffer (Noorain Eqbal)
- Do not audit capability check in x86 do_jit() (Ondrej Mosnacek)
- Fix arm64 JIT of BPF_ST insn when it writes into arena memory
(Puranjay Mohan)
* tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
bpf/arm64: Fix BPF_ST into arena memory
bpf: Make migrate_disable always inline to avoid partial inlining
bpf: Reject negative head_room in __bpf_skb_change_head
bpf: Conditionally include dynptr copy kfuncs
libbpf: Fix powerpc's stack register definition in bpf_tracing.h
bpf: Do not audit capability check in do_jit()
bpf: Sync pending IRQ work before freeing ring buffer
Fix bug where make nconfig doesn't initialize the default locale, which
causes ncurses menu borders to be displayed incorrectly (lqqqqk) in
UTF-8 terminals that don't support VT100 ACS by default, such as PuTTY.
Signed-off-by: Jakub Horký <jakub.git@horky.net>
Link: https://patch.msgid.link/20251014144405.3975275-2-jakub.git@horky.net
[nathan: Alphabetize locale.h include]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Pull drm fixes from Simona Vetter:
"Looks like stochastics conspired to make this one a bit bigger, but
nothing scary at all. Also first examples of the new Link: tags, yay!
Next week Dave should be back.
Drivers:
- mediatek: uaf in unbind, fixes -rc2 boot regression
- radeon: devm conversion fixes
- amdgpu: VPE idle handler, re-enable DM idle optimization, DCN3,
SMU, vblank, HDP eDP, powerplay fixes for fiji/iceland
- msm: bunch of gem error path fixes, gmu fw parsing fix, dpu fixes
- intel: fix dmc/dc6 asserts on ADL-S
- xe: fix xe_validation_guard(), wake device handling around gt reset
- ast: fix display output on AST2300
- etnaviv: fix gpu flush
- imx: fix parallel bridge handling
- nouveau: scheduler locking fix
- panel: fixes for kingdisplay-kd097d04 and sitronix-st7789v
Core Changes:
- CI: disable broken sanity job
- sysfb: fix NULL pointer access
- sched: fix SIGKILL handling, locking for race condition
- dma_fence: better timeline name for signalled fences"
* tag 'drm-fixes-2025-10-31' of https://gitlab.freedesktop.org/drm/kernel: (44 commits)
drm/ast: Clear preserved bits from register output value
drm/imx: parallel-display: add the bridge before attaching it
drm/imx: parallel-display: convert to devm_drm_bridge_alloc() API
drm/panel: kingdisplay-kd097d04: Disable EoTp
drm/panel: sitronix-st7789v: fix sync flags for t28cp45tn89
drm/xe: Do not wake device during a GT reset
drm/xe: Fix uninitialized return value from xe_validation_guard()
drm/msm/dpu: Fix adjusted mode clock check for 3d merge
drm/msm/dpu: Disable broken YUV on QSEED2 hardware
drm/msm/dpu: Require linear modifier for writeback framebuffers
drm/msm/dpu: Fix pixel extension sub-sampling
drm/msm/dpu: Disable scaling for unsupported scaler types
drm/msm/dpu: Propagate error from dpu_assign_plane_resources
drm/msm/dpu: Fix allocation of RGB SSPPs without scaling
drm/msm: dsi: fix PLL init in bonded mode
drm/i915/dmc: Clear HRR EVT_CTL/HTP to zero on ADL-S
drm/amd/display: Fix incorrect return of vblank enable on unconfigured crtc
drm/amd/display: Add HDR workaround for a specific eDP
drm/amdgpu: fix SPDX header on cyan_skillfish_reg_init.c
drm/amdgpu: fix SPDX header on irqsrcs_vcn_5_0.h
...
The arm64 JIT supports BPF_ST with BPF_PROBE_MEM32 (arena) by using the
tmp2 register to hold the dst + arena_vm_base value and using tmp2 as the
new dst register. But this is broken because in case is_lsi_offset()
returns false the tmp2 will be clobbered by emit_a64_mov_i(1, tmp2, off,
ctx); and hence the emitted store instruction will be of the form:
strb w10, [x11, x11]
Fix this by using the third temporary register to hold the dst +
arena_vm_base.
Fixes: 339af577ec05 ("bpf: Add arm64 JIT support for PROBE_MEM32 pseudo instructions.")
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20251030121715.55214-1-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Fix bug where make menuconfig doesn't initialize the default locale, which
causes ncurses menu borders to be displayed incorrectly (lqqqqk) in
UTF-8 terminals that don't support VT100 ACS by default, such as PuTTY.
Signed-off-by: Jakub Horký <jakub.git@horky.net>
Link: https://patch.msgid.link/20251014154933.3990990-1-jakub.git@horky.net
[nathan: Alphabetize locale.h include]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Pull pci fixes from Bjorn Helgaas:
- Restore custom qcom ASPM enablement code so L1 PM Substates are
enabled as they were in v6.17 even though the PCI core now enables
just L0s and L1 by default (Bjorn Helgaas)
- Size prefetchable bridge windows only when they actually exist, to
avoid a WARN_ON() regression (Ilpo Järvinen)
* tag 'pci-v6.18-fixes-4' of git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci:
PCI: Do not size non-existing prefetchable window
Revert "PCI: qcom: Remove custom ASPM enablement code"
Driver Changes:
- Fix xe_validation_guard() not guarding (Thomas Hellström)
- Do not wake device during a GT reset (Matthew Brost)
Signed-off-by: Simona Vetter <simona.vetter@ffwll.ch>
From: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patch.msgid.link/o2b3lucyitafbbcd5bewpfqnslavtnnpc6ck4qatnou2wwukix@rz6seyfw75uy
The build fails with llvm 21/22:
$ make LLVM=1 -j
...
LD vmlinux.o
GEN .vmlinux.objs
...
BTF .tmp_vmlinux1.btf.o
...
AS .tmp_vmlinux2.kallsyms.o
LD vmlinux.unstripped
BTFIDS vmlinux.unstripped
WARN: resolve_btfids: unresolved symbol migrate_enable
WARN: resolve_btfids: unresolved symbol migrate_disable
make[2]: *** [vmlinux.unstripped] Error 255
make[2]: *** Deleting file 'vmlinux.unstripped'
make[1]: *** [Makefile:1242: vmlinux] Error 2
make: *** [Makefile:248: __sub-make] Error 2
Two functions with identical names but different addresses are
considered ambiguous and removed by "pahole" from vmlinux BTF.
Later resolve_btfids warns since it cannot find them.
Commit 378b7708194f ("sched: Make migrate_{en,dis}able() inline") made
them inlineable in most places, but in vmlinux built with llvm 21 and 22
there are four symbols for migrate_{enable,disable}:
three static functions and one global function.
Fix the issue by marking migrate_{enable,disable} as always inline.
The alternative is to mark them as notrace/nokprobe which is more
drastic. Only bpf programs are prevented from attaching to these
functions. The rest of the tracing shouldn't be affected.
[note: Peter ok-ed the patch, Alexei rewrote commit log]
Fixes: 378b7708194f ("sched: Make migrate_{en,dis}able() inline")
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Menglong Dong <menglong.dong@linux.dev>
Link: https://lore.kernel.org/r/20251029183646.3811774-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Commit 5ff8c11775c7 ("KMSAN: Remove tautological checks") changed
CONFIG_HAVE_KMSAN_COMPILER from a dynamic check for
'-fsanitize=kernel-memory' to just being true for CONFIG_CC_IS_CLANG.
This missed the fact that not all architectures supported
'-fsanitize=kernel-memory' at the same time. For example, SystemZ / s390
gained support for KMSAN in clang-18 [1], so builds with clang-15
through clang-17 can select KMSAN but they error with:
clang-16: error: unsupported option '-fsanitize=kernel-memory' for target 's390x-unknown-linux-gnu'
Restore the cc-option check for '-fsanitize=kernel-memory' to make sure
the compiler target properly supports '-fsanitize=kernel-memory'. The
check for '-msan-disable-checks=1' does not need to be restored because
all supported clang versions for building the kernel support it.
Fixes: 5ff8c11775c7 ("KMSAN: Remove tautological checks")
Link: https://github.com/llvm/llvm-project/commit/a3e56a8792ffaf3a3d3538736e1042b8db45ab89 [1]
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202510220236.AVuXXCYy-lkp@intel.com/
Acked-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20251023-fix-kmsan-check-s390-clang-v1-1-4e6df477a4cc@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Pull VFIO fixes from Alex Williamson:
- Fix overflows in vfio type1 backend for mappings at the end of the
64-bit address space, resulting in leaked pinned memory.
New selftest support included to avoid such issues in the future
(Alex Mastro)
* tag 'vfio-v6.18-rc4' of https://github.com/awilliam/linux-vfio:
vfio: selftests: add end of address space DMA map/unmap tests
vfio: selftests: update DMA map/unmap helpers to support more test kinds
vfio/type1: handle DMA map/unmap up to the addressable limit
vfio/type1: move iova increment to unmap_unpin_*() caller
vfio/type1: sanitize for overflow using check_*_overflow()
pbus_size_mem() should only be called for bridge windows that exist but
__pci_bus_size_bridges() may point 'pref' to a resource that does not exist
(has zero flags) in case of non-root buses.
When prefetchable bridge window does not exist, the same non-prefetchable
bridge window is sized more than once which may result in duplicating
entries into the realloc_head list. Duplicated entries are shown in this
log and trigger a WARN_ON() because realloc_head had residual entries after
the resource assignment algorithm:
pci 0000:00:03.0: [11ab:6820] type 01 class 0x060400 PCIe Root Port
pci 0000:00:03.0: PCI bridge to [bus 00]
pci 0000:00:03.0: bridge window [io 0x0000-0x0fff]
pci 0000:00:03.0: bridge window [mem 0x00000000-0x000fffff]
pci 0000:00:03.0: bridge window [mem 0x00200000-0x003fffff] to [bus 02] add_size 200000 add_align 200000
pci 0000:00:03.0: bridge window [mem 0x00200000-0x003fffff] to [bus 02] add_size 200000 add_align 200000
pci 0000:00:03.0: bridge window [mem 0xe0000000-0xe03fffff]: assigned
pci 0000:00:03.0: PCI bridge to [bus 02]
pci 0000:00:03.0: bridge window [mem 0xe0000000-0xe03fffff]
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at drivers/pci/setup-bus.c:2373 pci_assign_unassigned_root_bus_resources+0x1bc/0x234
Check resource flags of 'pref' and only size the prefetchable window if the
resource has the IORESOURCE_PREFETCH flag.
Fixes: ae88d0b9c57f ("PCI: Use pbus_select_window_for_type() during mem window sizing")
Reported-by: Klaus Kudielka <klaus.kudielka@gmail.com>
Closes: https://lore.kernel.org/r/51e8cf1c62b8318882257d6b5a9de7fdaaecc343.camel@gmail.com/
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Klaus Kudielka <klaus.kudielka@gmail.com>
Link: https://patch.msgid.link/20251027132423.8841-1-ilpo.jarvinen@linux.intel.com
Short summary of fixes pull:
ast:
- Preserve correct bits on register I/O
dma-fence:
- Use correct timeline name
etnaviv:
- Use correct GPU adress space for flush
imx:
- parallel-display: Fix bridge handling
nouveau:
- Fix locking in scheduler
panel:
- kingdisplay-kd097d04: Disable EOT packet
- sitronix-st7789v: Use correct SYNC flags
sched:
- Fix locking to avoid race condition
- Fix SIGKILL handling
sysfb:
- Avoid NULL-pointer access
Signed-off-by: Simona Vetter <simona.vetter@ffwll.ch>
From: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20251030195644.GA188441@localhost.localdomain
Waking the device during a GT reset can lead to unintended memory
allocation, which is not allowed since GT resets occur in the reclaim
path. Prevent this by holding a PM reference while a reset is in flight.
Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Cc: stable@vger.kernel.org
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://lore.kernel.org/r/20251022005538.828980-3-matthew.brost@intel.com
(cherry picked from commit 480b358e7d8ef69fd8f1b0cad6e07c7d70a36ee4)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Yinhao et al. recently reported:
Our fuzzing tool was able to create a BPF program which triggered
the below BUG condition inside pskb_expand_head.
[ 23.016047][T10006] kernel BUG at net/core/skbuff.c:2232!
[...]
[ 23.017301][T10006] RIP: 0010:pskb_expand_head+0x1519/0x1530
[...]
[ 23.021249][T10006] Call Trace:
[ 23.021387][T10006] <TASK>
[ 23.021507][T10006] ? __pfx_pskb_expand_head+0x10/0x10
[ 23.021725][T10006] __bpf_skb_change_head+0x22a/0x520
[ 23.021939][T10006] bpf_skb_change_head+0x34/0x1b0
[ 23.022143][T10006] ___bpf_prog_run+0xf70/0xb670
[ 23.022342][T10006] __bpf_prog_run32+0xed/0x140
[...]
The problem is that in __bpf_skb_change_head() we need to reject a
negative head_room as otherwise this propagates all the way to the
pskb_expand_head() from skb_cow(). For example, if the BPF test infra
passes a skb with gso_skb:1 to the BPF helper with a negative head_room
of -22, then this gets passed into skb_cow(). __skb_cow() in this
example calculates a delta of -86 which gets aligned to -64, and then
triggers BUG_ON(nhead < 0). Thus, reject malformed negative input.
Fixes: 3a0af8fd61f9 ("bpf: BPF for lightweight tunnel infrastructure")
Reported-by: Yinhao Hu <dddddd@hust.edu.cn>
Reported-by: Kaiyan Mei <M202472210@hust.edu.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
Link: https://patch.msgid.link/20251023125532.182262-1-daniel@iogearbox.net
Previously linker scripts would always generate vmlinuz that has sections
aligned. And thus padded (correct Authenticode calculation) and unpadded
calculation would be same. As in https://github.com/rhboot/pesign userspace
tool would produce the same authenticode digest for both of the following
commands:
pesign --padding --hash --in ./arch/x86_64/boot/bzImage
pesign --nopadding --hash --in ./arch/x86_64/boot/bzImage
The commit 3e86e4d74c04 ("kbuild: keep .modinfo section in
vmlinux.unstripped") added .modinfo section of variable length. Depending
on kernel configuration it may or may not be aligned.
All userspace signing tooling correctly pads such section to calculation
spec compliant authenticode digest.
However, if bzImage is not further processed and is attempted to be loaded
directly by EDK2 firmware, it calculates unpadded Authenticode digest and
fails to correct accept/reject such kernel builds even when propoer
Authenticode values are enrolled in db/dbx. One can say EDK2 requires
aligned/padded kernels in Secureboot.
Thus add ALIGN(8) to the .modinfo section, to esure kernels irrespective of
modinfo contents can be loaded by all existing EDK2 firmware builds.
Fixes: 3e86e4d74c04 ("kbuild: keep .modinfo section in vmlinux.unstripped")
Cc: stable@vger.kernel.org
Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@surgut.co.uk>
Link: https://patch.msgid.link/20251026202100.679989-1-dimitri.ledkov@surgut.co.uk
Signed-off-by: Nathan Chancellor <nathan@kernel.org>