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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When commit fd81bc5cca8f ("scsi: device_handler: Return error pointer in
scsi_dh_attached_handler_name()") added code to fail parsing the path if
scsi_dh_attached_handler_name() failed with -ENOMEM, it didn't clean up
the reference to the path device that had just been taken. Fix this, and
steamline the error paths of parse_path() a little.
Fixes: fd81bc5cca8f ("scsi: device_handler: Return error pointer in scsi_dh_attached_handler_name()")
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Make several header functions static. Also remove
vdo_is_upgradable_version, which is unused.
Signed-off-by: Matthew Sakai <msakai@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
The origin bio carries blk-cgroup information which could be set from
foreground(task_css(css) - wbc->wb->blkcg_css), so the blkcg won't
control buffer io since commit ca522482e3eaf ("dm: pass NULL bdev to
bio_alloc_clone"). The synchronous io is still under control by blkcg,
because 'bio->bi_blkg' is set by io submitting task which has been added
into 'cgroup.procs'.
Fix it by using bio_clone_blkg_association when submitting a cloned bio.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=220985
Fixes: ca522482e3eaf ("dm: pass NULL bdev to bio_alloc_clone")
Reported-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Zhihao Cheng <chengzhihao1@huawei.com>
dm_exec_wrappedkey_op() passes through the derive_sw_secret, import_key,
generate_key, and prepare_key blk-crypto operations to an underlying
device.
Currently, it calls the operation on every underlying device until one
returns success.
This logic is flawed when the operation is expected to fail, such as an
invalid key being passed to derive_sw_secret. That can happen if
userspace passes an invalid key to the FS_IOC_ADD_ENCRYPTION_KEY ioctl.
When that happens on a device-mapper device that consists of many
dm-linear targets, a lot of unnecessary key unwrapping requests get sent
to the underlying key wrapping hardware.
Fix this by considering the first device only. As already documented in
the comment, it was already checked that all underlying devices support
wrapped keys, so this should be fine.
Fixes: e93912786e50 ("dm: pass through operations on wrapped inline crypto keys")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
The function "__init dm_verity_init" was calling "__exit
dm_verity_verify_sig_exit" and this triggered section mismatch error.
Fix this by dropping the "__exit" tag on dm_verity_verify_sig_exit.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 033724b1c627A ("dm-verity: add dm-verity keyring")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601210645.11u5Myme-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202601211041.pcTzwcdp-lkp@intel.com/
The "unstriped" device-mapper target incorrectly calculates the sector
offset on the mapped device when the target's origin is not zero.
Take for example this hypothetical concatenation of the members of a
two-disk RAID0:
linearized: 0 2097152 unstriped 2 128 0 /dev/md/raid0 0
linearized: 2097152 2097152 unstriped 2 128 1 /dev/md/raid0 0
The intent in this example is to create a single device named
/dev/mapper/linearized that comprises all of the chunks of the first disk
of the RAID0 set, followed by all of the chunks of the second disk of the
RAID0 set.
This fails because dm-unstripe.c's map_to_core function does its
computations based on the sector number within the mapper device rather
than the sector number within the target. The bug turns invisible when
the target's origin is at sector zero of the mapper device, as is the
common case. In the example above, however, what happens is that the
first half of the mapper device gets mapped correctly to the first disk
of the RAID0, but the second half of the mapper device gets mapped past
the end of the RAID0 device, and accesses to any of those sectors return
errors.
Signed-off-by: Matt Whitlock <kernel@mattwhitlock.name>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 18a5bf270532 ("dm: add unstriped target")
There's a logic quirk in the handling of suspend in the bitmap mode:
This is the sequence of calls if we are reloading a dm-integrity table:
* dm_integrity_ctr reads a superblock with the flag SB_FLAG_DIRTY_BITMAP
set.
* dm_integrity_postsuspend initializes a journal and clears the flag
SB_FLAG_DIRTY_BITMAP.
* dm_integrity_resume sees the superblock with SB_FLAG_DIRTY_BITMAP set -
thus it interprets the journal as if it were a bitmap.
This quirk causes recalculation problem if the user increases the size of
the device in the bitmap mode.
Fix this by reading a fresh copy on the superblock in
dm_integrity_resume. This commit also fixes another logic quirk - the
branch that sets bitmap bits if the device was extended should only be
executed if the flag SB_FLAG_DIRTY_BITMAP is set.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: Ondrej Kozina <okozina@redhat.com>
Fixes: 468dfca38b1a ("dm integrity: add a bitmap mode")
Cc: stable@vger.kernel.org
dm-bufio's map from block number to buffer is organized as a hash table
of red-black trees. It does far more lookups in this hash table than
necessary: typically one lookup to lock the tree, one lookup to search
the tree, and one lookup to unlock the tree. Only one of those lookups
is needed. Optimize it to do only the minimum number of lookups.
This improves performance. It also reduces the object code size,
considering that the redundant hash table lookups were being inlined.
For example, the size of the text section of dm-bufio.o decreases from
15599 to 15070 bytes with gcc 15 and x86_64, or from 20652 to 20244
bytes with clang 21 and arm64.
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Merge cache_put() into its only caller, cache_put_and_wake().
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Add selftests that verify the keyring behaves correctly.
For simplicity this works with dm-verity as a module.
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Add a dedicated ".dm-verity" keyring for root hash signature
verification, similar to the ".fs-verity" keyring used by fs-verity.
By default the keyring is unused retaining the exact same old behavior.
For systems that provision additional keys only intended for dm-verity
images during boot, the dm_verity.keyring_unsealed=1 kernel parameter
leaves the keyring open.
We want to use this in systemd as a way add keys during boot that are
only used for creating dm-verity devices for later mounting and nothing
else. The discoverable disk image (DDI) spec at [1] heavily relies on
dm-verity and we would like to expand this even more. This will allow us
to do that in a fully backward compatible way.
Once provisioning is complete, userspace restricts and activates it for
dm-verity verification. If userspace fully seals the keyring then it
gains the guarantee that no new keys can be added.
Link: https://uapi-group.org/specifications/specs/discoverable_partitions_specification [1]
Co-developed-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Stale rq->bio values have been observed to cause double-initialization of
cloned bios in request-based device-mapper targets, leading to
use-after-free and double-free scenarios.
One such case occurs when using dm-multipath on top of a PCIe NVMe
namespace, where cloned request bios are freed during
blk_complete_request(), but rq->bio is left intact. Subsequent clone
teardown then attempts to free the same bios again via
blk_rq_unprep_clone().
The resulting double-free path looks like:
nvme_pci_complete_batch()
nvme_complete_batch()
blk_mq_end_request_batch()
blk_complete_request() // called on a DM clone request
bio_endio() // first free of all clone bios
...
rq->end_io() // end_clone_request()
dm_complete_request(tio->orig)
dm_softirq_done()
dm_done()
dm_end_request()
blk_rq_unprep_clone() // second free of clone bios
Fix this by clearing the clone request's bio pointer when the last cloned
bio completes, ensuring that later teardown paths do not attempt to free
already-released bios.
Signed-off-by: Michael Liang <mliang@purestorage.com>
Reviewed-by: Mohamed Khalfella <mkhalfella@purestorage.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Replace obsolete mentions of "tasklets" with "softirq context", and
"workqueue" with "kworker".
This reflects the fact that the implementation of the
"try_verify_in_tasklet" dm-verity option now accesses softirq context
using either the BH workqueue API or inline execution, not the tasklet
API. The old names conflated the API with the intended execution
context, so they became outdated when the APIs changed.
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
dm-verity doesn't support data blocks that span pages, and it sets
dma_alignment accordingly. As such, instead of using
bio_advance_iter(), it can use the more lightweight function
bio_advance_iter_single() to get the same result.
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Since each dm_verity_io is never on both the BH and normal workqueues at
the same time, there's no need for two different work_structs. Replace
the 'bh_work' and 'work' fields with just 'work'.
Note: this is correct even though it means 'work' may be reused while
verity_bh_work() is running. The workqueue API allows work functions to
reuse or free their work_struct, and many workqueue users rely on that.
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This continues the effort to refactor workqueue APIs, which began with
the introduction of new workqueues and a new alloc_workqueue flag in:
commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")
The refactoring is going to alter the default behavior of
alloc_workqueue() to be unbound by default.
With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU. For more details see the Link tag below.
In order to keep alloc_workqueue() behavior identical, explicitly request
WQ_PERCPU.
Link: https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>