Calling kmem_obj_info() on KFENCE objects has been producing garbage data due to the object not actually being maintained by SLAB or SLUB. Fix this by asking KFENCE to copy missing KFENCE-specific information to struct kmem_obj_info when the object was allocated by KFENCE. Link: https://lore.kernel.org/all/20220323090520.GG16885@xsang-OptiPlex-9020/ Fixes: b89fb5ef0ce6 ("mm, kfence: insert KFENCE hooks for SLUB") Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB") Reported-by: kernel test robot <oliver.sang@xxxxxxxxx> Signed-off-by: Marco Elver <elver@xxxxxxxxxx> --- include/linux/kfence.h | 22 ++++++++++++++++++++++ mm/kfence/core.c | 21 --------------------- mm/kfence/kfence.h | 21 +++++++++++++++++++++ mm/kfence/report.c | 34 ++++++++++++++++++++++++++++++++++ mm/slab.c | 4 ++++ mm/slub.c | 4 ++++ 6 files changed, 85 insertions(+), 21 deletions(-) diff --git a/include/linux/kfence.h b/include/linux/kfence.h index f49e64222628..4a7c633cb219 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -204,6 +204,23 @@ static __always_inline __must_check bool kfence_free(void *addr) */ bool __must_check kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs *regs); +#ifdef CONFIG_PRINTK +struct kmem_obj_info; +/** + * kfence_kmem_obj_info() - fill kmem_obj_info struct + * @kpp: kmem_obj_info to be filled + * @object: the object + * + * Return: + * * false - not a KFENCE object + * * true - a KFENCE object and filled @kpp + * + * Copies information to @kpp that kmem_obj_info() is unable to populate for + * KFENCE objects. + */ +bool kfence_kmem_obj_info(struct kmem_obj_info *kpp, void *object); +#endif + #else /* CONFIG_KFENCE */ static inline bool is_kfence_address(const void *addr) { return false; } @@ -221,6 +238,11 @@ static inline bool __must_check kfence_handle_page_fault(unsigned long addr, boo return false; } +#ifdef CONFIG_PRINTK +struct kmem_obj_info; +static inline bool kfence_kmem_obj_info(struct kmem_obj_info *kpp, void *object) { return false; } +#endif + #endif #endif /* _LINUX_KFENCE_H */ diff --git a/mm/kfence/core.c b/mm/kfence/core.c index a203747ad2c0..9b2b5f56f4ae 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -231,27 +231,6 @@ static bool kfence_unprotect(unsigned long addr) return !KFENCE_WARN_ON(!kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), false)); } -static inline struct kfence_metadata *addr_to_metadata(unsigned long addr) -{ - long index; - - /* The checks do not affect performance; only called from slow-paths. */ - - if (!is_kfence_address((void *)addr)) - return NULL; - - /* - * May be an invalid index if called with an address at the edge of - * __kfence_pool, in which case we would report an "invalid access" - * error. - */ - index = (addr - (unsigned long)__kfence_pool) / (PAGE_SIZE * 2) - 1; - if (index < 0 || index >= CONFIG_KFENCE_NUM_OBJECTS) - return NULL; - - return &kfence_metadata[index]; -} - static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *meta) { unsigned long offset = (meta - kfence_metadata + 1) * PAGE_SIZE * 2; diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h index 9a6c4b1b12a8..600f2e2431d6 100644 --- a/mm/kfence/kfence.h +++ b/mm/kfence/kfence.h @@ -96,6 +96,27 @@ struct kfence_metadata { extern struct kfence_metadata kfence_metadata[CONFIG_KFENCE_NUM_OBJECTS]; +static inline struct kfence_metadata *addr_to_metadata(unsigned long addr) +{ + long index; + + /* The checks do not affect performance; only called from slow-paths. */ + + if (!is_kfence_address((void *)addr)) + return NULL; + + /* + * May be an invalid index if called with an address at the edge of + * __kfence_pool, in which case we would report an "invalid access" + * error. + */ + index = (addr - (unsigned long)__kfence_pool) / (PAGE_SIZE * 2) - 1; + if (index < 0 || index >= CONFIG_KFENCE_NUM_OBJECTS) + return NULL; + + return &kfence_metadata[index]; +} + /* KFENCE error types for report generation. */ enum kfence_error_type { KFENCE_ERROR_OOB, /* Detected a out-of-bounds access. */ diff --git a/mm/kfence/report.c b/mm/kfence/report.c index f93a7b2a338b..5887fa610c9d 100644 --- a/mm/kfence/report.c +++ b/mm/kfence/report.c @@ -273,3 +273,37 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r /* We encountered a memory safety error, taint the kernel! */ add_taint(TAINT_BAD_PAGE, LOCKDEP_STILL_OK); } + +#ifdef CONFIG_PRINTK +static void kfence_to_kp_stack(const struct kfence_track *track, void **kp_stack) +{ + int i, j; + + i = get_stack_skipnr(track->stack_entries, track->num_stack_entries, NULL); + for (j = 0; i < track->num_stack_entries && j < KS_ADDRS_COUNT - 1; ++i, ++j) + kp_stack[j] = (void *)track->stack_entries[i]; + kp_stack[j] = NULL; +} + +bool kfence_kmem_obj_info(struct kmem_obj_info *kpp, void *object) +{ + const struct kfence_metadata *meta = addr_to_metadata((unsigned long)object); + + if (!meta) + return false; + + /* Requesting info an a never-used object is almost certainly a bug. */ + if (WARN_ON(meta->state == KFENCE_OBJECT_UNUSED)) + return true; + + kpp->kp_objp = (void *)meta->addr; + + kfence_to_kp_stack(&meta->alloc_track, kpp->kp_stack); + if (meta->state == KFENCE_OBJECT_FREED) + kfence_to_kp_stack(&meta->free_track, kpp->kp_free_stack); + /* get_stack_skipnr() ensures the first entry is outside allocator. */ + kpp->kp_ret = kpp->kp_stack[0]; + + return true; +} +#endif diff --git a/mm/slab.c b/mm/slab.c index b04e40078bdf..4d44b094e0ab 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -3675,6 +3675,10 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab) kpp->kp_slab = slab; cachep = slab->slab_cache; kpp->kp_slab_cache = cachep; + + if (kfence_kmem_obj_info(kpp, object)) + return; + objp = object - obj_offset(cachep); kpp->kp_data_offset = obj_offset(cachep); slab = virt_to_slab(objp); diff --git a/mm/slub.c b/mm/slub.c index 74d92aa4a3a2..c7d2cfd60b87 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4325,6 +4325,10 @@ void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab) kpp->kp_ptr = object; kpp->kp_slab = slab; kpp->kp_slab_cache = s; + + if (kfence_kmem_obj_info(kpp, object)) + return; + base = slab_address(slab); objp0 = kasan_reset_tag(object); #ifdef CONFIG_SLUB_DEBUG -- 2.35.1.1094.g7c7d902a7c-goog
