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
Clone this repository
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
This patch implements delayed allocation (delalloc) in ntfs3 driver.
It introduces an in-memory delayed-runlist (run_da) and the helpers to
track, reserve and later convert those delayed reservations into real
clusters at writeback time. The change keeps on-disk formats untouched and
focuses on pagecache integration, correctness and safe interaction with
fallocate, truncate, and dio/iomap paths.
Key points:
- add run_da (delay-allocated run tree) and bookkeeping for delayed clusters.
- mark ranges as delalloc (DELALLOC_LCN) instead of immediately allocating.
Actual allocation performed later (writeback / attr_set_size_ex / explicit
flush paths).
- direct i/o / iomap paths updated to avoid dio collisions with
delalloc: dio falls back or forces allocation of delayed blocks before
proceeding.
- punch/collapse/truncate/fallocate check and cancel delay-alloc reservations.
Sparse/compressed files handled specially.
- free-space checks updated (ntfs_check_free_space) to account for reserved
delalloc clusters and MFT record budgeting.
- delayed allocations are committed on last writer (file release) and on
explicit allocation flush paths.
Tested-by: syzbot@syzkaller.appspotmail.com
Reported-by: syzbot+2bd8e813c7f767aa9bb1@syzkaller.appspotmail.com
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
When ntfs_read_run_nb_ra() is invoked with run == NULL the code later
assumes run is valid and may call run_get_entry(NULL, ...), and also
uses clen/idx without initializing them. Smatch reported uninitialized
variable warnings and this can lead to undefined behaviour. This patch
fixes it.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202512230646.v5hrYXL0-lkp@intel.com/
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Add fall-through to fix the warning in ntfs_fs_parse_param().
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202602041402.uojBz5QY-lkp@intel.com/
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
This patch improves mount option parsing by allowing explicit boolean
values for acl and prealloc. Previously those options were exposed only
as presence/absence flags.
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
In the 'DeleteIndexEntryRoot' case of the 'do_action' function, the
entry size ('esize') is retrieved from the log record without adequate
bounds checking.
Specifically, the code calculates the end of the entry ('e2') using:
e2 = Add2Ptr(e1, esize);
It then calculates the size for memmove using 'PtrOffset(e2, ...)',
which subtracts the end pointer from the buffer limit. If 'esize' is
maliciously large, 'e2' exceeds the used buffer size. This results in
a negative offset which, when cast to size_t for memmove, interprets
as a massive unsigned integer, leading to a heap buffer overflow.
This commit adds a check to ensure that the entry size ('esize') strictly
fits within the remaining used space of the index header before performing
memory operations.
Fixes: b46acd6a6a62 ("fs/ntfs3: Add NTFS journal")
Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Clang warns (or errors with CONFIG_WERROR=y):
fs/ntfs3/inode.c:1021:6: error: variable 'folio' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
1021 | if (is_resident(ni)) {
| ^~~~~~~~~~~~~~~
fs/ntfs3/inode.c:1024:48: note: uninitialized use occurs here
1024 | while ((folio = writeback_iter(mapping, wbc, folio, &err)))
| ^~~~~
folio should be initialized to NULL for the first iteration of
writeback_iter() to start the loop properly. Restore the NULL
initialization of folio that was lost in the recent iomap conversion to
clear up the warning.
Fixes: 099ef9a ("fs/ntfs3: implement iomap-based file operations")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/oe-kbuild-all/202601010644.FIhOXy6Y-lkp@intel.com/
Closes: https://lore.kernel.org/r/202601010513.axd56bks-lkp@intel.com/
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
[almaz.alexandrovich@paragon-software.com: added a few more tags]
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Extract the repeated pattern of duplicating attribute and updating
OpenAttr into a helper function to reduce code duplication and improve
maintainability.
Signed-off-by: Baolin Liu <liubaolin@kylinos.cn>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
When processing valid within the range [valid : pos), if valid cannot
be retrieved correctly, for example, if the retrieved valid value is
always the same, this can trigger a potential infinite loop, similar
to the hung problem reported by syzbot [1].
Adding a check for the valid value within the loop body, and terminating
the loop and returning -EINVAL if the value is the same as the current
value, can prevent this.
[1]
INFO: task syz.4.21:6056 blocked for more than 143 seconds.
Call Trace:
rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
inode_lock include/linux/fs.h:1027 [inline]
ntfs_file_write_iter+0xe6/0x870 fs/ntfs3/file.c:1284
Fixes: 4342306f0f0d ("fs/ntfs3: Add file operations and implementation")
Reported-by: syzbot+bcf9e1868c1a0c7e04f1@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=bcf9e1868c1a0c7e04f1
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Fix below sparse warnings:
fs/ntfs3/inode.c:972:34: sparse: sparse: symbol 'ntfs_writeback_ops' was not declared.
Should it be static?
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601061424.nbKLNwC5-lkp@intel.com/
Signed-off-by: sunliming <sunliming@kylinos.cn>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Syzbot reported a circular locking dependency between wnd->rw_lock
(sbi->used.bitmap) and ni->file.run_lock.
The deadlock scenario:
1. ntfs_extend_mft() takes ni->file.run_lock then wnd->rw_lock.
2. run_unpack_ex() takes wnd->rw_lock then tries to acquire
ni->file.run_lock inside ntfs_refresh_zone().
This creates an AB-BA deadlock.
Fix this by using down_read_trylock() instead of down_read() when
acquiring run_lock in run_unpack_ex(). If the lock is contended,
skip ntfs_refresh_zone() - the MFT zone will be refreshed on the
next MFT operation. This breaks the circular dependency since we
never block waiting for run_lock while holding wnd->rw_lock.
Reported-by: syzbot+d27edf9f96ae85939222@syzkaller.appspotmail.com
Tested-by: syzbot+d27edf9f96ae85939222@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d27edf9f96ae85939222
Signed-off-by: Szymon Wilczek <swilczek.lx@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
This patch modifies the ntfs3 driver by replacing the buffer_head-based
operations with the iomap ones.
Implementation details:
- Implements core iomap operations (ntfs_iomap_begin/end) for block mapping:
Proper handling of resident attributes via IOMAP_INLINE.
Support for sparse files through IOMAP_HOLE semantics.
Correct unwritten extent handling for zeroing operations.
- Replaces custom implementations with standardized iomap helpers:
Converts buffered reads to use iomap_read_folio and iomap_readahead.
Implements iomap_file_buffered_write for write operations.
Uses iomap_dio_rw for direct I/O paths.
Migrates zero range operations to iomap_zero_range.
- Preserves special handling paths for compressed files
- Implements proper EOF/valid data size management during writes
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Syzbot reported a task hung in ni_readpage_cmpr (now ni_read_folio_cmpr).
This is caused by a lock inversion deadlock involving the inode mutex
(ni_lock) and page locks.
Scenario:
1. Task A enters ntfs_read_folio() for page X. It acquires ni_lock.
2. Task A calls ni_read_folio_cmpr(), which attempts to lock all pages in
the compressed frame (including page Y).
3. Concurrently, Task B (e.g., via readahead) has locked page Y and
calls ntfs_read_folio().
4. Task B waits for ni_lock (held by A).
5. Task A waits for page Y lock (held by B).
-> DEADLOCK.
The fix is to restructure locking: do not take ni_lock in ntfs_read_folio().
Instead, acquire ni_lock inside ni_read_folio_cmpr() ONLY AFTER all required
page locks for the frame have been successfully acquired. This restores the
correct lock ordering (Page Lock -> ni_lock) consistent with VFS.
Reported-by: syzbot+5af33dd272b913b65880@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5af33dd272b913b65880
Fixes: f35590ee26f5 ("fs/ntfs3: remove ntfs_bio_pages and use page cache for compressed I/O")
Signed-off-by: Szymon Wilczek <swilczek.lx@gmail.com>
[almaz.alexandrovich@paragon-software.com: ni_readpage_cmpr was renamed to ni_read_folio_cmpr]
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
The generic llseek implementation does not understand ntfs data runs,
sparse regions, or compression semantics, and therefore cannot correctly
locate data or holes in files.
Add a filesystem-specific llseek handler that scans attribute data runs
to find the next data or hole starting at the given offset. Handle
resident attributes, sparse runs, compressed holes, and the implicit hole
at end-of-file.
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Handle ntfs_read_folio() early when the folio offset is beyond i_valid
by zero-filling the folio and marking it uptodate. This avoids needless
I/O and locking, improves read performance.
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
If attr_set_size() fails while truncating down, the error is silently
ignored and the inode may be left in an inconsistent state.
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Do not keep preallocated clusters for sparsed and compressed files.
Preserving preallocation in these cases causes fsx failures when running
with sparse files and preallocation enabled.
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>