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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The current netlink and /proc interfaces deviate from their traditional
values when dynamic threading is enabled, and there is currently no way
to know what the current setting is. This patch brings the reporting
back in line with traditional behavior.
Make these interfaces report the requested maximum number of threads
instead of the number currently running. Also, update documentation and
comments to reflect that this value represents a maximum and not the
number currently running.
Fixes: d8316b837c2c ("nfsd: add controls to set the minimum number of threads per pool")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
nfsd_nl_listener_set_doit() uses get_current_cred() without
put_cred().
As we can see from other callers, svc_xprt_create_from_sa()
does not require the extra refcount.
nfsd_nl_listener_set_doit() is always in the process context,
sendmsg(), and current->cred does not go away.
Let's use current_cred() in nfsd_nl_listener_set_doit().
Fixes: 16a471177496 ("NFSD: add listener-{set,get} netlink command")
Cc: stable@vger.kernel.org
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
syzbot reported memory leak of struct cred. [0]
nfsd_nl_threads_set_doit() passes get_current_cred() to
nfsd_svc(), but put_cred() is not called after that.
The cred is finally passed down to _svc_xprt_create(),
which calls get_cred() with the cred for struct svc_xprt.
The ownership of the refcount by get_current_cred() is not
transferred to anywhere and is just leaked.
nfsd_svc() is also called from write_threads(), but it does
not bump file->f_cred there.
nfsd_nl_threads_set_doit() is called from sendmsg() and
current->cred does not go away.
Let's use current_cred() in nfsd_nl_threads_set_doit().
[0]:
BUG: memory leak
unreferenced object 0xffff888108b89480 (size 184):
comm "syz-executor", pid 5994, jiffies 4294943386
hex dump (first 32 bytes):
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace (crc 369454a7):
kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
slab_post_alloc_hook mm/slub.c:4958 [inline]
slab_alloc_node mm/slub.c:5263 [inline]
kmem_cache_alloc_noprof+0x412/0x580 mm/slub.c:5270
prepare_creds+0x22/0x600 kernel/cred.c:185
copy_creds+0x44/0x290 kernel/cred.c:286
copy_process+0x7a7/0x2870 kernel/fork.c:2086
kernel_clone+0xac/0x6e0 kernel/fork.c:2651
__do_sys_clone+0x7f/0xb0 kernel/fork.c:2792
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xa4/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Fixes: 924f4fb003ba ("NFSD: convert write_threads to netlink command")
Cc: stable@vger.kernel.org
Reported-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69744674.a00a0220.33ccc7.0000.GAE@google.com/
Tested-by: syzbot+dd3b43aa0204089217ee@syzkaller.appspotmail.com
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Now that infrastructure for NFSv4 POSIX draft ACL has been added
to NFSD, it should be safe to advertise support to NFS clients.
NFSD_SUPPATTR_EXCLCREAT_WORD2 includes NFSv4.2-only attributes,
but version filtering occurs via nfsd_suppattrs[] before this
mask is applied, ensuring pre-4.2 clients never see unsupported
attributes.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The POSIX ACL extension to NFSv4 enables clients to set access
and default ACLs via FATTR4_POSIX_ACCESS_ACL and
FATTR4_POSIX_DEFAULT_ACL attributes. Integration of these
attributes into SETATTR processing requires wiring them through
the nfsd_attrs structure and ensuring proper cleanup on all
code paths.
This patch connects the na_pacl and na_dpacl fields in
nfsd_attrs to the decoded ACL pointers from the NFSv4 SETATTR
decoder. Ownership of these ACL references transfers to attrs
immediately after initialization, with the decoder's pointers
cleared to NULL. This transfer ensures nfsd_attrs_free()
releases the ACLs on normal completion, while new error paths
call posix_acl_release() directly when cleanup occurs before
nfsd_attrs_free() runs.
Early returns in the nfsd4_setattr() function gain conversions
to goto statements that branch to proper cleanup handlers.
Error paths before fh_want_write() branch to out_err for ACL
release only; paths after fh_want_write() use the existing out
label for full cleanup via nfsd_attrs_free().
The patch adds mutual exclusion between NFSv4 ACLs (sa_acl) and
POSIX ACLs. Setting both types simultaneously returns
nfserr_inval because these ACL models cannot coexist on the
same file object.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
NFSv4.2 clients can specify POSIX draft ACLs when creating file
objects via OPEN(CREATE) and CREATE operations. The previous patch
added POSIX ACL support to the NFSv4 SETATTR operation for modifying
existing objects, but file creation follows different code paths
that also require POSIX ACL handling.
This patch integrates POSIX ACL support into nfsd4_create() and
nfsd4_create_file(). Ownership of the decoded ACL pointers
(op_dpacl, op_pacl, cr_dpacl, cr_pacl) transfers to the nfsd_attrs
structure immediately, with the original fields cleared to NULL.
This transfer ensures nfsd_attrs_free() releases the ACLs upon
completion while preventing double-free on error paths.
Mutual exclusion between NFSv4 ACLs and POSIX ACLs is enforced:
setting both op_acl and op_dpacl/op_pacl simultaneously returns
nfserr_inval. Errors during ACL application clear the corresponding
bits in the result bitmask (fattr->bmval), signaling partial
completion to the client.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The POSIX ACL extension to NFSv4 defines FATTR4_POSIX_ACCESS_ACL
and FATTR4_POSIX_DEFAULT_ACL for setting access and default ACLs
via CREATE, OPEN, and SETATTR operations. This patch adds the XDR
decoders for those attributes.
The nfsd4_decode_fattr4() function gains two additional parameters
for receiving decoded POSIX ACLs. CREATE, OPEN, and SETATTR
decoders pass pointers to these new parameters, enabling clients
to set POSIX ACLs during object creation or modification.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Support for FATTR4_POSIX_ACCESS_ACL and FATTR4_POSIX_DEFAULT_ACL
attributes in subsequent patches allows clients to set both ACL
types simultaneously during SETATTR and file creation. Each ACL
type can succeed or fail independently, requiring the server to
clear individual attribute bits in the reply bitmap when one
fails while the other succeeds.
The existing na_aclerr field cannot distinguish which ACL type
encountered an error. Separate error fields (na_paclerr for
access ACLs, na_dpaclerr for default ACLs) enable the server to
report per-ACL-type failures accurately.
This refactoring also adds validation previously absent: default
ACL processing rejects non-directory targets with EINVAL and
passes NULL to set_posix_acl() when a_count is zero to delete
the ACL. Access ACL processing rejects zero a_count with EINVAL
for ACL_SCOPE_FILE_SYSTEM semantics (the only scope currently
supported).
The changes preserve compatibility with existing NFSv4 ACL code.
NFSv4 ACL conversion (nfs4_acl_nfsv4_to_posix()) never produces
POSIX ACLs with a_count == 0, so the new validation logic only
affects future POSIX ACL attribute handling.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Section 9.3 of draft-ietf-nfsv4-posix-acls-00 prohibits use of
the POSIX ACL attributes with VERIFY and NVERIFY operations: the
server MUST reply NFS4ERR_INVAL when a client attempts this.
Beyond the protocol requirement, comparison of POSIX draft ACLs
via (N)VERIFY presents an implementation challenge. Clients are
not required to order the ACEs within a POSIX ACL in any
particular way, making reliable attribute comparison impractical.
Return nfserr_inval when the client requests FATTR4_POSIX_ACCESS_ACL
or FATTR4_POSIX_DEFAULT_ACL in a VERIFY or NVERIFY operation.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The POSIX ACL extension to NFSv4 defines FATTR4_POSIX_ACCESS_ACL
for retrieving the access ACL of a file or directory. This patch
adds the XDR encoder for that attribute.
The access ACL is retrieved via get_inode_acl(). If the filesystem
provides no explicit access ACL, one is synthesized from the file
mode via posix_acl_from_mode(). Each entry is encoded as a
posixace4: tag type, permission bits, and principal name (empty
for structural entries, resolved via idmapping for USER/GROUP
entries).
Unlike the default ACL encoder which applies only to directories,
this encoder handles all inode types and ensures an access ACL is
always available through mode-based synthesis when needed.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The POSIX ACL extension to NFSv4 defines FATTR4_POSIX_DEFAULT_ACL
for retrieving a directory's default ACL. This patch adds the
XDR encoder for that attribute.
For directories, the default ACL is retrieved via get_inode_acl()
and each entry is encoded as a posixace4: tag type, permission
bits, and principal name (empty for structural entries like
USER_OBJ/GROUP_OBJ/MASK/OTHER, resolved via idmapping for
USER/GROUP entries).
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The FATTR4_ACL_TRUEFORM_SCOPE attribute indicates the granularity at
which the ACL model can vary: per file object, per file system, or
uniformly across the entire server.
In Linux, the ACL model is determined by the SB_POSIXACL superblock
flag, which applies uniformly to all files within a file system.
Different exported file systems can have different ACL models, but
individual files cannot differ from their containing file system.
ACL_SCOPE_FILE_SYSTEM accurately reflects this behavior.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Mapping between NFSv4 ACLs and POSIX ACLs is semantically imprecise:
a client that sets an NFSv4 ACL and reads it back may see a different
ACL than it wrote. The proposed NFSv4 POSIX ACL extension introduces
the FATTR4_ACL_TRUEFORM attribute, which reports whether a file
object stores its access control permissions using NFSv4 ACLs or
POSIX ACLs.
A client aware of this extension can avoid lossy translation by
requesting and setting ACLs in their native format.
When NFSD is built with CONFIG_NFSD_V4_POSIX_ACLS, report
ACL_MODEL_POSIX_DRAFT for file objects on file systems with the
SB_POSIXACL flag set, and ACL_MODEL_NONE otherwise. Linux file
systems do not store NFSv4 ACLs natively, so ACL_MODEL_NFS4 is never
reported.
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
The language definition was extracted from the new
draft-ietf-nfsv4-posix-acls specification. This ensures good
constant and type name alignment between the spec and the Linux
kernel source code, and brings in some basic XDR utilities for
handling NFSv4 POSIX draft ACLs.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
A new IETF draft extends NFSv4.2 with POSIX ACL attributes:
https://www.ietf.org/archive/id/draft-ietf-nfsv4-posix-acls-00.txt
This draft has not yet been ratified. A build-time configuration
option allows developers and distributors to decide whether to
expose this experimental protocol extension to NFSv4 clients. The
option is disabled by default to prevent unintended deployment of
potentially unstable protocol features in production environments.
This approach mirrors the existing NFSD_V4_DELEG_TIMESTAMPS option,
which gates another experimental NFSv4 extension based on an
unratified IETF draft.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
XDR specification files can contain lines prefixed with '%' that
pass through unchanged to generated output. Traditional rpcgen
removes the '%' and emits the remainder verbatim, allowing direct
insertion of C includes, pragma directives, or other language-
specific content into the generated code.
Until now, xdrgen silently discarded these lines during parsing.
This prevented specifications from including necessary headers or
preprocessor directives that might be required for the generated
code to compile correctly.
The grammar now captures pass-through lines instead of ignoring
them. A new AST node type represents pass-through content, and
the AST transformer strips the leading '%' character. Definition
and source generators emit pass-through content in document order,
preserving the original placement within the specification.
This brings xdrgen closer to feature parity with traditional
rpcgen while maintaining the existing document-order processing
model.
Existing generated xdrgen source code has been regenerated.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>