[PATCH 11/11] kobject: Require explicit initialization of struct kobj_type::release

[Ian Rogers <irogers@google.com>]

Documentation/core-api/kobject.rst states:

  "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. Note that the kernel will warn you if you forget to provide a
  release() method. Do not try to get rid of this warning by providing an
  "empty" release function."

Annotate struct kobj_type::release with __require_explicit_initialization
so the compiler diagnoses any struct kobj_type initializer that omits
.release.

For the remaining legacy struct kobj_type definitions where the kobject
is static, per-CPU, or embedded inside a devm- or parent-managed
structure rather than freed by kobject_put(), explicitly initialize
.release = NULL with a comment documenting why no release callback is
provided.

Link: https://lpc.events/event/20/contributions/2392/
Assisted-by: Antigravity:gemini-3.1-pro
Signed-off-by: Ian Rogers <irogers@google.com>
---
 arch/arm64/kernel/cpuinfo.c                          | 2 ++
 drivers/acpi/sysfs.c                                 | 2 ++
 drivers/dma/ioat/sysfs.c                             | 2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c              | 4 ++++
 drivers/infiniband/hw/hfi1/sysfs.c                   | 2 ++
 drivers/infiniband/hw/usnic/usnic_ib_sysfs.c         | 2 ++
 drivers/parisc/pdc_stable.c                          | 2 ++
 drivers/power/supply/ab8500_fg.c                     | 2 ++
 drivers/soc/hisilicon/kunpeng_hccs.c                 | 6 ++++++
 drivers/video/fbdev/omap2/omapfb/dss/display-sysfs.c | 2 ++
 drivers/video/fbdev/omap2/omapfb/dss/manager-sysfs.c | 2 ++
 drivers/video/fbdev/omap2/omapfb/dss/overlay-sysfs.c | 2 ++
 fs/erofs/sysfs.c                                     | 4 ++++
 fs/f2fs/sysfs.c                                      | 6 ++++++
 fs/ocfs2/cluster/masklog.c                           | 2 ++
 include/linux/kobject.h                              | 2 +-
 16 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 45c63f3d75c5..ab78efdb13f5 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -309,6 +309,8 @@ const struct seq_operations cpuinfo_op = {
 
 
 static const struct kobj_type cpuregs_kobj_type = {
+	/* info->kobj is embedded in per-CPU cpu_data; cpuid_cpu_offline() only calls kobject_del(). */
+	.release = NULL,
 	.sysfs_ops = &kobj_sysfs_ops,
 };
 
diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index dd4a99f09efe..7534d3f305ba 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -972,6 +972,8 @@ static struct attribute *hotplug_profile_attrs[] = {
 ATTRIBUTE_GROUPS(hotplug_profile);
 
 static const struct kobj_type acpi_hotplug_profile_ktype = {
+	/* hotplug->kobj is embedded in static struct acpi_scan_hotplug objects. */
+	.release = NULL,
 	.sysfs_ops = &kobj_sysfs_ops,
 	.default_groups = hotplug_profile_groups,
 };
diff --git a/drivers/dma/ioat/sysfs.c b/drivers/dma/ioat/sysfs.c
index e796ddb5383f..7fdd0ca36b98 100644
--- a/drivers/dma/ioat/sysfs.c
+++ b/drivers/dma/ioat/sysfs.c
@@ -167,6 +167,8 @@ static const struct attribute *const ioat_attrs[] = {
 ATTRIBUTE_GROUPS(ioat);
 
 const struct kobj_type ioat_ktype = {
+	/* ioatdma_chan is allocated via devm_kzalloc() rather than freed by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &ioat_sysfs_ops,
 	.default_groups = ioat_groups,
 };
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
index b15af318784b..0477468f12ae 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
@@ -789,6 +789,8 @@ static const struct sysfs_ops xcp_cfg_res_sysfs_ops = {
 };
 
 static const struct kobj_type xcp_cfg_res_sysfs_ktype = {
+	/* xcp_res is embedded in struct amdgpu_xcp_cfg rather than freed individually by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &xcp_cfg_res_sysfs_ops,
 	.default_groups = xcp_cfg_res_sysfs_groups,
 };
@@ -1053,6 +1055,8 @@ static const struct attribute_group amdgpu_xcp_attrs_group = {
 };
 
 static const struct kobj_type xcp_sysfs_ktype = {
+	/* xcp is embedded in struct amdgpu_xcp_mgr rather than freed individually by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &kobj_sysfs_ops,
 };
 
diff --git a/drivers/infiniband/hw/hfi1/sysfs.c b/drivers/infiniband/hw/hfi1/sysfs.c
index 372cfd13dc61..33b26650069d 100644
--- a/drivers/infiniband/hw/hfi1/sysfs.c
+++ b/drivers/infiniband/hw/hfi1/sysfs.c
@@ -608,6 +608,8 @@ static const struct sysfs_ops sde_sysfs_ops = {
 };
 
 static struct kobj_type sde_ktype = {
+	/* sdma_engine is embedded in the dd->per_sdma array rather than freed by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &sde_sysfs_ops,
 };
 
diff --git a/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c b/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
index fdb63a8fb997..234d8d9532aa 100644
--- a/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
+++ b/drivers/infiniband/hw/usnic/usnic_ib_sysfs.c
@@ -245,6 +245,8 @@ static struct attribute *usnic_ib_qpn_default_attrs[] = {
 ATTRIBUTE_GROUPS(usnic_ib_qpn_default);
 
 static struct kobj_type usnic_ib_qpn_type = {
+	/* usnic_ib_qp_grp is embedded in RDMA core-managed struct usnic_ib_qp_grp. */
+	.release = NULL,
 	.sysfs_ops = &usnic_ib_qpn_sysfs_ops,
 	.default_groups = usnic_ib_qpn_default_groups,
 };
diff --git a/drivers/parisc/pdc_stable.c b/drivers/parisc/pdc_stable.c
index 16f4496bca95..6d972c965c1e 100644
--- a/drivers/parisc/pdc_stable.c
+++ b/drivers/parisc/pdc_stable.c
@@ -484,6 +484,8 @@ ATTRIBUTE_GROUPS(paths_subsys);
 
 /* Specific kobject type for our PDC paths */
 static const struct kobj_type ktype_pdcspath = {
+	/* pdcspath_entry instances are static; lifetime is not controlled by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &pdcspath_attr_ops,
 	.default_groups = paths_subsys_groups,
 };
diff --git a/drivers/power/supply/ab8500_fg.c b/drivers/power/supply/ab8500_fg.c
index e6b5efdf5dc9..206ee2e392fb 100644
--- a/drivers/power/supply/ab8500_fg.c
+++ b/drivers/power/supply/ab8500_fg.c
@@ -2531,6 +2531,8 @@ static struct attribute *ab8500_fg_attrs[] = {
 ATTRIBUTE_GROUPS(ab8500_fg);
 
 static const struct kobj_type ab8500_fg_ktype = {
+	/* fg_kobject is embedded in devm-allocated struct ab8500_fg; ab8500_fg_sysfs_exit() only calls kobject_del(). */
+	.release = NULL,
 	.sysfs_ops = &ab8500_fg_sysfs_ops,
 	.default_groups = ab8500_fg_groups,
 };
diff --git a/drivers/soc/hisilicon/kunpeng_hccs.c b/drivers/soc/hisilicon/kunpeng_hccs.c
index 0cc2953d59a5..5d083d2b72ca 100644
--- a/drivers/soc/hisilicon/kunpeng_hccs.c
+++ b/drivers/soc/hisilicon/kunpeng_hccs.c
@@ -1038,6 +1038,8 @@ static struct attribute *hccs_port_default_attrs[] = {
 ATTRIBUTE_GROUPS(hccs_port_default);
 
 static const struct kobj_type hccs_port_type = {
+	/* hccs_port_info is allocated via devm_kcalloc() rather than freed by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &hccs_comm_ops,
 	.default_groups = hccs_port_default_groups,
 };
@@ -1110,6 +1112,8 @@ static struct attribute *hccs_die_default_attrs[] = {
 ATTRIBUTE_GROUPS(hccs_die_default);
 
 static const struct kobj_type hccs_die_type = {
+	/* hccs_die_info is allocated via devm_kcalloc() rather than freed by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &hccs_comm_ops,
 	.default_groups = hccs_die_default_groups,
 };
@@ -1213,6 +1217,8 @@ static struct attribute *hccs_chip_default_attrs[] = {
 ATTRIBUTE_GROUPS(hccs_chip_default);
 
 static const struct kobj_type hccs_chip_type = {
+	/* hccs_chip_info is allocated via devm_kcalloc() rather than freed by kobject_put(). */
+	.release = NULL,
 	.sysfs_ops = &hccs_comm_ops,
 	.default_groups = hccs_chip_default_groups,
 };
diff --git a/drivers/video/fbdev/omap2/omapfb/dss/display-sysfs.c b/drivers/video/fbdev/omap2/omapfb/dss/display-sysfs.c
index ae937854403b..3d787245f5b5 100644
--- a/drivers/video/fbdev/omap2/omapfb/dss/display-sysfs.c
+++ b/drivers/video/fbdev/omap2/omapfb/dss/display-sysfs.c
@@ -304,6 +304,8 @@ static const struct sysfs_ops display_sysfs_ops = {
 };
 
 static struct kobj_type display_ktype = {
+	/* dssdev->kobj is embedded in struct omap_dss_device and zeroed in display_uninit_sysfs(). */
+	.release = NULL,
 	.sysfs_ops = &display_sysfs_ops,
 	.default_groups = display_sysfs_groups,
 };
diff --git a/drivers/video/fbdev/omap2/omapfb/dss/manager-sysfs.c b/drivers/video/fbdev/omap2/omapfb/dss/manager-sysfs.c
index 1b644be5fe2e..cf816e83e903 100644
--- a/drivers/video/fbdev/omap2/omapfb/dss/manager-sysfs.c
+++ b/drivers/video/fbdev/omap2/omapfb/dss/manager-sysfs.c
@@ -496,6 +496,8 @@ static const struct sysfs_ops manager_sysfs_ops = {
 };
 
 static struct kobj_type manager_ktype = {
+	/* mgr->kobj is embedded in static managers[] and zeroed in dss_manager_kobj_uninit(). */
+	.release = NULL,
 	.sysfs_ops = &manager_sysfs_ops,
 	.default_groups = manager_sysfs_groups,
 };
diff --git a/drivers/video/fbdev/omap2/omapfb/dss/overlay-sysfs.c b/drivers/video/fbdev/omap2/omapfb/dss/overlay-sysfs.c
index 1da4fb1c77b4..9aa16b3dee5e 100644
--- a/drivers/video/fbdev/omap2/omapfb/dss/overlay-sysfs.c
+++ b/drivers/video/fbdev/omap2/omapfb/dss/overlay-sysfs.c
@@ -429,6 +429,8 @@ static const struct sysfs_ops overlay_sysfs_ops = {
 };
 
 static struct kobj_type overlay_ktype = {
+	/* ovl->kobj is embedded in static overlays[]; dss_overlay_kobj_uninit() only calls kobject_del(). */
+	.release = NULL,
 	.sysfs_ops = &overlay_sysfs_ops,
 	.default_groups = overlay_sysfs_groups,
 };
diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index dfcec9376cd5..588d541e1713 100644
--- a/fs/erofs/sysfs.c
+++ b/fs/erofs/sysfs.c
@@ -238,6 +238,8 @@ static const struct kobj_type erofs_sb_ktype = {
 static const struct kobj_type erofs_ktype = {
 	.default_groups = erofs_groups,
 	.sysfs_ops	= &erofs_attr_ops,
+	/* erofs_root is a static struct kset; lifetime is not controlled by kobject_put(). */
+	.release	= NULL,
 };
 
 static struct kset erofs_root = {
@@ -247,6 +249,8 @@ static struct kset erofs_root = {
 static const struct kobj_type erofs_feat_ktype = {
 	.default_groups = erofs_feat_groups,
 	.sysfs_ops	= &erofs_attr_ops,
+	/* erofs_feat is a static struct kobject; lifetime is not controlled by kobject_put(). */
+	.release	= NULL,
 };
 
 static struct kobject erofs_feat = {
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 811e350a1430..a66cef927c62 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -1653,6 +1653,8 @@ static const struct kobj_type f2fs_sb_ktype = {
 
 static const struct kobj_type f2fs_ktype = {
 	.sysfs_ops	= &f2fs_attr_ops,
+	/* f2fs_kset is a static struct kset; lifetime is not controlled by kobject_put(). */
+	.release	= NULL,
 };
 
 static struct kset f2fs_kset = {
@@ -1667,6 +1669,8 @@ static const struct sysfs_ops f2fs_feat_attr_ops = {
 static const struct kobj_type f2fs_feat_ktype = {
 	.default_groups = f2fs_feat_groups,
 	.sysfs_ops	= &f2fs_feat_attr_ops,
+	/* f2fs_feat is a static struct kobject; lifetime is not controlled by kobject_put(). */
+	.release	= NULL,
 };
 
 static struct kobject f2fs_feat = {
@@ -1681,6 +1685,8 @@ static const struct sysfs_ops f2fs_tune_attr_ops = {
 static const struct kobj_type f2fs_tune_ktype = {
 	.default_groups = f2fs_tune_groups,
 	.sysfs_ops	= &f2fs_tune_attr_ops,
+	/* f2fs_tune is a static struct kobject; lifetime is not controlled by kobject_put(). */
+	.release	= NULL,
 };
 
 static struct kobject f2fs_tune = {
diff --git a/fs/ocfs2/cluster/masklog.c b/fs/ocfs2/cluster/masklog.c
index 563881ddbf00..e476fa7ffea6 100644
--- a/fs/ocfs2/cluster/masklog.c
+++ b/fs/ocfs2/cluster/masklog.c
@@ -147,6 +147,8 @@ static const struct sysfs_ops mlog_attr_ops = {
 static struct kobj_type mlog_ktype = {
 	.default_groups = mlog_default_groups,
 	.sysfs_ops      = &mlog_attr_ops,
+	/* mlog_kset is a static struct kset; lifetime is not controlled by kobject_put(). */
+	.release        = NULL,
 };
 
 static struct kset mlog_kset = {
diff --git a/include/linux/kobject.h b/include/linux/kobject.h
index 55e37a5d405e..e65331717e03 100644
--- a/include/linux/kobject.h
+++ b/include/linux/kobject.h
@@ -114,7 +114,7 @@ void kobject_get_ownership(const struct kobject *kobj, kuid_t *uid, kgid_t *gid)
 char *kobject_get_path(const struct kobject *kobj, gfp_t flag);
 
 struct kobj_type {
-	void (*release)(struct kobject *kobj);
+	void (*release)(struct kobject *kobj) __require_explicit_initialization;
 	const struct sysfs_ops *sysfs_ops;
 	const struct attribute_group **default_groups;
 	const struct kobj_ns_type_operations *(*child_ns_type)(const struct kobject *kobj);
-- 
2.56.0.385.gd3acb90ef8-goog