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 __must_init 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, permanent firmware structures, 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. Where the existing teardown is not safe with CONFIG_DEBUG_KOBJECT_RELEASE, because the kobject's memory can be freed or cleared while the delayed kobject cleanup is still pending (ioat, kunpeng_hccs and omapfb display), the comment says so. Fixing those is left to follow-up patches; this change does not alter their behavior. Link: https://lpc.events/event/20/contributions/2392/ Signed-off-by: Ian Rogers <[email protected]> --- arch/arm64/kernel/cpuinfo.c | 5 +++++ drivers/acpi/sysfs.c | 2 ++ 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/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 +++++ fs/erofs/sysfs.c | 10 +++++++++ fs/f2fs/sysfs.c | 15 +++++++++++++ fs/ocfs2/cluster/masklog.c | 5 +++++ include/linux/kobject.h | 2 +- 18 files changed, 117 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c index 94e6cd211d70..7a4ac8dd0b86 100644 --- a/arch/arm64/kernel/cpuinfo.c +++ b/arch/arm64/kernel/cpuinfo.c @@ -295,6 +295,11 @@ const struct seq_operations cpuinfo_op = { static const struct kobj_type cpuregs_kobj_type = { + /* + * Pre-existing: 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 a99373547126..1948b80e8a4a 100644 --- a/drivers/acpi/sysfs.c +++ b/drivers/acpi/sysfs.c @@ -973,6 +973,8 @@ static struct attribute *hotplug_profile_attrs[] = { ATTRIBUTE_GROUPS(hotplug_profile); static const struct kobj_type acpi_hotplug_profile_ktype = { + /* Pre-existing: 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..5ba44876eb96 100644 --- a/drivers/dma/ioat/sysfs.c +++ b/drivers/dma/ioat/sysfs.c @@ -167,6 +167,13 @@ static const struct attribute *const ioat_attrs[] = { ATTRIBUTE_GROUPS(ioat); const struct kobj_type ioat_ktype = { + /* + * Pre-existing: ioatdma_chan is freed by release_ioatdma(), not + * by kobject_put(). With CONFIG_DEBUG_KOBJECT_RELEASE the delayed + * kobject cleanup queued by ioat_kobject_del() may run after + * that kfree(), a use-after-free. + */ + .release = NULL, .sysfs_ops = &ioat_sysfs_ops, .default_groups = ioat_groups, }; diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c index 17888cf54447..c2cccd924b03 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ualink.c @@ -885,6 +885,11 @@ static const struct attribute_group ualink_xcp_info_group = { }; static const struct kobj_type ualink_xcp_info_ktype = { + /* + * Pre-existing: xcp->ualink.kobj 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/gpu/drm/amd/amdgpu/amdgpu_xcp.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c index ab14079d1c42..0847134a1391 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c @@ -797,6 +797,11 @@ static const struct sysfs_ops xcp_cfg_res_sysfs_ops = { }; static const struct kobj_type xcp_cfg_res_sysfs_ktype = { + /* + * Pre-existing: 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, }; @@ -1061,6 +1066,11 @@ static const struct attribute_group amdgpu_xcp_attrs_group = { }; static const struct kobj_type xcp_sysfs_ktype = { + /* + * Pre-existing: 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..5a1aca06b542 100644 --- a/drivers/infiniband/hw/hfi1/sysfs.c +++ b/drivers/infiniband/hw/hfi1/sysfs.c @@ -608,6 +608,11 @@ static const struct sysfs_ops sde_sysfs_ops = { }; static struct kobj_type sde_ktype = { + /* + * Pre-existing: sdma_engine is embedded in 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..df0e48070c2e 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 = { + /* Pre-existing: 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 6b567a74fc2c..2f530e8c6757 100644 --- a/drivers/parisc/pdc_stable.c +++ b/drivers/parisc/pdc_stable.c @@ -484,6 +484,11 @@ ATTRIBUTE_GROUPS(paths_subsys); /* Specific kobject type for our PDC paths */ static const struct kobj_type ktype_pdcspath = { + /* + * Pre-existing: 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..d62411e4f535 100644 --- a/drivers/power/supply/ab8500_fg.c +++ b/drivers/power/supply/ab8500_fg.c @@ -2531,6 +2531,11 @@ static struct attribute *ab8500_fg_attrs[] = { ATTRIBUTE_GROUPS(ab8500_fg); static const struct kobj_type ab8500_fg_ktype = { + /* + * Pre-existing: 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/s390/char/sclp_mem.c b/drivers/s390/char/sclp_mem.c index 6df1926d4c62..2fb7271dce36 100644 --- a/drivers/s390/char/sclp_mem.c +++ b/drivers/s390/char/sclp_mem.c @@ -305,6 +305,8 @@ static ssize_t sclp_memmap_on_memory_store(struct kobject *kobj, struct kobj_att } static const struct kobj_type ktype = { + /* Pre-existing: permanent firmware kobjects, never freed */ + .release = NULL, .sysfs_ops = &kobj_sysfs_ops, }; diff --git a/drivers/soc/hisilicon/kunpeng_hccs.c b/drivers/soc/hisilicon/kunpeng_hccs.c index 0cc2953d59a5..da7a64c95058 100644 --- a/drivers/soc/hisilicon/kunpeng_hccs.c +++ b/drivers/soc/hisilicon/kunpeng_hccs.c @@ -1038,6 +1038,13 @@ static struct attribute *hccs_port_default_attrs[] = { ATTRIBUTE_GROUPS(hccs_port_default); static const struct kobj_type hccs_port_type = { + /* + * Pre-existing: hccs_port_info is allocated via devm_kzalloc() + * rather than freed by kobject_put(). With + * CONFIG_DEBUG_KOBJECT_RELEASE the delayed kobject cleanup may run + * after devm frees it on unbind, a use-after-free. + */ + .release = NULL, .sysfs_ops = &hccs_comm_ops, .default_groups = hccs_port_default_groups, }; @@ -1110,6 +1117,13 @@ static struct attribute *hccs_die_default_attrs[] = { ATTRIBUTE_GROUPS(hccs_die_default); static const struct kobj_type hccs_die_type = { + /* + * Pre-existing: hccs_die_info is allocated via devm_kzalloc() + * rather than freed by kobject_put(). With + * CONFIG_DEBUG_KOBJECT_RELEASE the delayed kobject cleanup may run + * after devm frees it on unbind, a use-after-free. + */ + .release = NULL, .sysfs_ops = &hccs_comm_ops, .default_groups = hccs_die_default_groups, }; @@ -1213,6 +1227,13 @@ static struct attribute *hccs_chip_default_attrs[] = { ATTRIBUTE_GROUPS(hccs_chip_default); static const struct kobj_type hccs_chip_type = { + /* + * Pre-existing: hccs_chip_info is allocated via devm_kzalloc() + * rather than freed by kobject_put(). With + * CONFIG_DEBUG_KOBJECT_RELEASE the delayed kobject cleanup may run + * after devm frees it on unbind, a use-after-free. + */ + .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..452920a4e2a9 100644 --- a/drivers/video/fbdev/omap2/omapfb/dss/display-sysfs.c +++ b/drivers/video/fbdev/omap2/omapfb/dss/display-sysfs.c @@ -304,6 +304,13 @@ static const struct sysfs_ops display_sysfs_ops = { }; static struct kobj_type display_ktype = { + /* + * Pre-existing: dssdev->kobj is embedded in struct omap_dss_device + * and zeroed in display_uninit_sysfs() right after kobject_put(). + * With CONFIG_DEBUG_KOBJECT_RELEASE that memset() clobbers the + * pending delayed kobject cleanup. + */ + .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..40ec750f4315 100644 --- a/drivers/video/fbdev/omap2/omapfb/dss/manager-sysfs.c +++ b/drivers/video/fbdev/omap2/omapfb/dss/manager-sysfs.c @@ -496,6 +496,11 @@ static const struct sysfs_ops manager_sysfs_ops = { }; static struct kobj_type manager_ktype = { + /* + * Pre-existing: 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..4d333031b18d 100644 --- a/drivers/video/fbdev/omap2/omapfb/dss/overlay-sysfs.c +++ b/drivers/video/fbdev/omap2/omapfb/dss/overlay-sysfs.c @@ -429,6 +429,11 @@ static const struct sysfs_ops overlay_sysfs_ops = { }; static struct kobj_type overlay_ktype = { + /* + * Pre-existing: ovl->kobj is embedded in static overlays[]; + * dss_overlay_kobj_uninit() drops the kobject ref. + */ + .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..2ea6773cd98f 100644 --- a/fs/erofs/sysfs.c +++ b/fs/erofs/sysfs.c @@ -238,6 +238,11 @@ static const struct kobj_type erofs_sb_ktype = { static const struct kobj_type erofs_ktype = { .default_groups = erofs_groups, .sysfs_ops = &erofs_attr_ops, + /* + * Pre-existing: erofs_root is a static struct kset; lifetime + * is not controlled by kobject_put(). + */ + .release = NULL, }; static struct kset erofs_root = { @@ -247,6 +252,11 @@ static struct kset erofs_root = { static const struct kobj_type erofs_feat_ktype = { .default_groups = erofs_feat_groups, .sysfs_ops = &erofs_attr_ops, + /* + * Pre-existing: 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 430356e500af..6e15695cb75f 100644 --- a/fs/f2fs/sysfs.c +++ b/fs/f2fs/sysfs.c @@ -1683,6 +1683,11 @@ static const struct kobj_type f2fs_sb_ktype = { static const struct kobj_type f2fs_ktype = { .sysfs_ops = &f2fs_attr_ops, + /* + * Pre-existing: f2fs_kset is a static struct kset; lifetime + * is not controlled by kobject_put(). + */ + .release = NULL, }; static struct kset f2fs_kset = { @@ -1697,6 +1702,11 @@ 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, + /* + * Pre-existing: f2fs_feat is a static struct kobject; lifetime + * is not controlled by kobject_put(). + */ + .release = NULL, }; static struct kobject f2fs_feat = { @@ -1711,6 +1721,11 @@ 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, + /* + * Pre-existing: 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..ff8a1cf51e72 100644 --- a/fs/ocfs2/cluster/masklog.c +++ b/fs/ocfs2/cluster/masklog.c @@ -147,6 +147,11 @@ static const struct sysfs_ops mlog_attr_ops = { static struct kobj_type mlog_ktype = { .default_groups = mlog_default_groups, .sysfs_ops = &mlog_attr_ops, + /* + * Pre-existing: 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..8a1332030884 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) __must_init; 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); -- 2.56.0.313.g2479322e68-goog
