[PATCH v2 0/9] Add __must_init and require explicit kobj_type::release

[Ian Rogers <irogers@google.com>]

Clang supports the 'require_explicit_initialization' attribute on struct
fields to enforce that the field is explicitly initialized when an
aggregate object is constructed, emitting -Wuninitialized-explicit-init
(enabled by default) if the field is omitted.

Following discussion at the Linux Plumbers Conference [1], patch 1 adds
the attribute to include/linux/compiler_attributes.h as __must_init. In
v1 it was called __require_explicit_initialization. Kees picked up that
patch with a first seq_file user [2], and in that thread Greg suggested
the shorter __must_init spelling, which Kees and Miguel agreed to. As
the attribute did not land in the v7.4 merge window, Kees asked that
this series carry the renamed attribute. The Acked-by/Reviewed-by tags
on patch 1 were given for the original spelling; the rename is
mechanical.

As Documentation/core-api/kobject.rst notes:
  "One important point cannot be overstated: every kobject must have a
  release() method, and the kobject must persist (in a consistent state)
  until that method is called. If these constraints are not met, the
  code is flawed."

Annotating struct kobj_type::release caught struct kobj_type definitions
across the tree that omitted .release:
- Patches 2-8 fix struct kobj_type definitions where dynamically
  allocated kobjects, ksets, or enclosing structures were either leaked
  on kobject_put(), freed prematurely before kobject release, or missing
  proper static initializers.
- Patch 9 annotates struct kobj_type::release with __must_init and
  explicitly sets .release = NULL (with explanatory comments prefixed
  with "Pre-existing:") on the remaining legacy struct kobj_type
  definitions whose kobjects are static, per-CPU, permanent firmware
  structures, or embedded in devm- or parent-managed structures.

Note on tool use: An LLM coding assistant was used to help audit the
compiler diagnostics across the tree, draft the fixes and changelog
descriptions, and verify builds and review feedback.

Changes in v2:
- Rebased on v7.3-16928-g83f32c773255 (v7.4 merge window).
- Patch 1: Rename __require_explicit_initialization to __must_init per
  Greg Kroah-Hartman; document the Clang >= 20 requirement per Miguel
  Ojeda; note the Clang gap for file-scope objects without an
  initializer reported by Kees Cook; add tags from v1 and from Kees's
  posting.
- Move LLM assistance attribution from Assisted-by tags to this cover
  letter per commit 1e035297ffda ("docs: remove Assisted-by
  references").
- Patch 4 (cpufreq): Use "cpufreq: governor:" prefix, drop Fixes tag,
  fix typo, and remove the redundant runtime assignment in
  cpufreq_dbs_governor_init() per Zhongqiu Han.
- Dropped v1 patch 5 (ACPI: CPPC), already fixed upstream by
  commit 27954e29d7de ("ACPI: CPPC: Release CPC descriptors through
  kobject").
- Patch 5 (dlm): Call kobject_del() before dlm_recoverd_stop() in
  release_lockspace() and the new_lockspace() error path, and wait on a
  new ls_kobj_done completion before freeing the lockspace or dropping
  the module reference, avoiding races with delayed kobject release.
- Dropped v1 patch 8 (s390/sclp_mem) per Sumanth Korikkar: the
  /sys/firmware/memory/memoryX kobjects are permanent, so sclp_mem.c is
  folded into patch 9 with .release = NULL.
- Patch 7 (ubifs): Add Tested-by and Reviewed-by from Zhihao Cheng.
- Patch 8 (drm/amdkfd): Check q->kobj.state_in_sysfs before
  kobject_del() in kfd_procfs_del_queue().
- Patch 9 (kobject): Cover sclp_mem.c and the new amdgpu_ualink.c
  ualink_xcp_info_ktype, fix the overlay-sysfs.c comment, and prefix
  legacy .release = NULL comments with "Pre-existing:".
- Patch 9 (kobject): The ioat, kunpeng_hccs and omapfb display comments
  now say that the existing teardown can use-after-free under
  CONFIG_DEBUG_KOBJECT_RELEASE (reported by Sashiko). Fixing those
  drivers is left to follow-up patches.

v1: https://lore.kernel.org/all/20261013223946.1836757-1-irogers@google.com/
[1] https://lpc.events/event/20/contributions/2392/
[2] https://lore.kernel.org/lkml/20261014225811.i.852-kees@kernel.org/

Ian Rogers (9):
  Compiler Attributes: Add __must_init macro
  powerpc/secvar: Add missing kobject release callback to secvar_ktype
  sh: sq: Add missing kobject release callback to ktype_percpu_entry
  cpufreq: governor: Initialize kobj_type release callback statically
  dlm: Free dlm_ls in kobject release callback
  xen/sys-hypervisor: Add release callback to hyp_sysfs_kobj_type
  ubifs: sysfs: Use kset_create_and_add() for ubifs_kset
  drm/amdkfd: Free queue in procfs_queue_type kobject release callback
  kobject: Require explicit initialization of struct kobj_type::release

 Documentation/conf.py                         |  1 +
 arch/arm64/kernel/cpuinfo.c                   |  5 ++++
 arch/powerpc/kernel/secvar-sysfs.c            |  6 +++++
 arch/sh/kernel/cpu/sh4/sq.c                   |  6 +++++
 drivers/acpi/sysfs.c                          |  2 ++
 drivers/cpufreq/cpufreq_conservative.c        |  5 +++-
 drivers/cpufreq/cpufreq_governor.c            |  4 +--
 drivers/cpufreq/cpufreq_governor.h            |  1 +
 drivers/cpufreq/cpufreq_ondemand.c            |  5 +++-
 drivers/dma/ioat/sysfs.c                      |  7 +++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c    |  5 ++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c       | 10 +++++++
 drivers/gpu/drm/amd/amdkfd/kfd_process.c      | 12 ++++++---
 drivers/gpu/drm/amd/amdkfd/kfd_queue.c        |  5 +++-
 drivers/infiniband/hw/hfi1/sysfs.c            |  5 ++++
 drivers/infiniband/hw/usnic/usnic_ib_sysfs.c  |  2 ++
 drivers/parisc/pdc_stable.c                   |  5 ++++
 drivers/power/supply/ab8500_fg.c              |  5 ++++
 drivers/s390/char/sclp_mem.c                  |  2 ++
 drivers/soc/hisilicon/kunpeng_hccs.c          | 21 +++++++++++++++
 .../fbdev/omap2/omapfb/dss/display-sysfs.c    |  7 +++++
 .../fbdev/omap2/omapfb/dss/manager-sysfs.c    |  5 ++++
 .../fbdev/omap2/omapfb/dss/overlay-sysfs.c    |  5 ++++
 drivers/xen/sys-hypervisor.c                  |  6 +++++
 fs/dlm/dlm_internal.h                         |  1 +
 fs/dlm/lockspace.c                            | 26 ++++++++++++++-----
 fs/erofs/sysfs.c                              | 10 +++++++
 fs/f2fs/sysfs.c                               | 15 +++++++++++
 fs/ocfs2/cluster/masklog.c                    |  5 ++++
 fs/ubifs/sysfs.c                              | 24 +++++------------
 include/linux/compiler_attributes.h           | 12 +++++++++
 include/linux/kobject.h                       |  2 +-
 scripts/checkpatch.pl                         |  1 +
 tools/lib/python/kdoc/xforms_lists.py         |  1 +
 34 files changed, 202 insertions(+), 32 deletions(-)


base-commit: 83f32c773255720a661aa45d83e36278135f23f5
-- 
2.56.0.313.g2479322e68-goog


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