mm, kfence: support kmem_dump_obj() for KFENCE objects
Calling kmem_obj_info() via kmem_dump_obj() on KFENCE objects has been producing garbage data due to the object not actually being maintained by SLAB or SLUB. Fix this by implementing __kfence_obj_info() that copies relevant information to struct kmem_obj_info when the object was allocated by KFENCE; this is called by a common kmem_obj_info(), which also calls the slab/slub/slob specific variant now called __kmem_obj_info(). For completeness, kmem_dump_obj() now displays if the object was allocated by KFENCE. Link: https://lore.kernel.org/all/20220323090520.GG16885@xsang-OptiPlex-9020/ Link: https://lkml.kernel.org/r/20220406131558.3558585-1-elver@google.com Fixes:b89fb5ef0c
("mm, kfence: insert KFENCE hooks for SLUB") Fixes:d3fb45f370
("mm, kfence: insert KFENCE hooks for SLAB") Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Reported-by: kernel test robot <oliver.sang@intel.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> [slab] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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2dfe63e61c
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@ -204,6 +204,22 @@ static __always_inline __must_check bool kfence_free(void *addr)
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*/
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bool __must_check kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs *regs);
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#ifdef CONFIG_PRINTK
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struct kmem_obj_info;
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/**
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* __kfence_obj_info() - fill kmem_obj_info struct
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* @kpp: kmem_obj_info to be filled
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* @object: the object
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*
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* Return:
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* * false - not a KFENCE object
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* * true - a KFENCE object, filled @kpp
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*
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* Copies information to @kpp for KFENCE objects.
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*/
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bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab);
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#endif
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#else /* CONFIG_KFENCE */
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static inline bool is_kfence_address(const void *addr) { return false; }
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@ -221,6 +237,14 @@ static inline bool __must_check kfence_handle_page_fault(unsigned long addr, boo
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return false;
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}
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#ifdef CONFIG_PRINTK
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struct kmem_obj_info;
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static inline bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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{
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return false;
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}
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#endif
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#endif
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#endif /* _LINUX_KFENCE_H */
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@ -231,27 +231,6 @@ static bool kfence_unprotect(unsigned long addr)
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return !KFENCE_WARN_ON(!kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), false));
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}
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static inline struct kfence_metadata *addr_to_metadata(unsigned long addr)
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{
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long index;
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/* The checks do not affect performance; only called from slow-paths. */
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if (!is_kfence_address((void *)addr))
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return NULL;
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/*
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* May be an invalid index if called with an address at the edge of
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* __kfence_pool, in which case we would report an "invalid access"
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* error.
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*/
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index = (addr - (unsigned long)__kfence_pool) / (PAGE_SIZE * 2) - 1;
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if (index < 0 || index >= CONFIG_KFENCE_NUM_OBJECTS)
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return NULL;
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return &kfence_metadata[index];
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}
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static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *meta)
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{
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unsigned long offset = (meta - kfence_metadata + 1) * PAGE_SIZE * 2;
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@ -96,6 +96,27 @@ struct kfence_metadata {
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extern struct kfence_metadata kfence_metadata[CONFIG_KFENCE_NUM_OBJECTS];
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static inline struct kfence_metadata *addr_to_metadata(unsigned long addr)
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{
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long index;
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/* The checks do not affect performance; only called from slow-paths. */
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if (!is_kfence_address((void *)addr))
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return NULL;
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/*
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* May be an invalid index if called with an address at the edge of
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* __kfence_pool, in which case we would report an "invalid access"
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* error.
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*/
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index = (addr - (unsigned long)__kfence_pool) / (PAGE_SIZE * 2) - 1;
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if (index < 0 || index >= CONFIG_KFENCE_NUM_OBJECTS)
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return NULL;
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return &kfence_metadata[index];
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}
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/* KFENCE error types for report generation. */
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enum kfence_error_type {
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KFENCE_ERROR_OOB, /* Detected a out-of-bounds access. */
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@ -273,3 +273,50 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r
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/* We encountered a memory safety error, taint the kernel! */
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add_taint(TAINT_BAD_PAGE, LOCKDEP_STILL_OK);
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}
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#ifdef CONFIG_PRINTK
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static void kfence_to_kp_stack(const struct kfence_track *track, void **kp_stack)
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{
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int i, j;
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i = get_stack_skipnr(track->stack_entries, track->num_stack_entries, NULL);
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for (j = 0; i < track->num_stack_entries && j < KS_ADDRS_COUNT; ++i, ++j)
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kp_stack[j] = (void *)track->stack_entries[i];
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if (j < KS_ADDRS_COUNT)
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kp_stack[j] = NULL;
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}
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bool __kfence_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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{
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struct kfence_metadata *meta = addr_to_metadata((unsigned long)object);
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unsigned long flags;
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if (!meta)
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return false;
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/*
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* If state is UNUSED at least show the pointer requested; the rest
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* would be garbage data.
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*/
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kpp->kp_ptr = object;
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/* Requesting info an a never-used object is almost certainly a bug. */
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if (WARN_ON(meta->state == KFENCE_OBJECT_UNUSED))
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return true;
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raw_spin_lock_irqsave(&meta->lock, flags);
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kpp->kp_slab = slab;
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kpp->kp_slab_cache = meta->cache;
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kpp->kp_objp = (void *)meta->addr;
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kfence_to_kp_stack(&meta->alloc_track, kpp->kp_stack);
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if (meta->state == KFENCE_OBJECT_FREED)
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kfence_to_kp_stack(&meta->free_track, kpp->kp_free_stack);
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/* get_stack_skipnr() ensures the first entry is outside allocator. */
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kpp->kp_ret = kpp->kp_stack[0];
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raw_spin_unlock_irqrestore(&meta->lock, flags);
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return true;
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}
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#endif
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@ -3665,7 +3665,7 @@ EXPORT_SYMBOL(__kmalloc_node_track_caller);
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#endif /* CONFIG_NUMA */
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#ifdef CONFIG_PRINTK
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void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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{
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struct kmem_cache *cachep;
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unsigned int objnr;
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@ -868,7 +868,7 @@ struct kmem_obj_info {
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void *kp_stack[KS_ADDRS_COUNT];
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void *kp_free_stack[KS_ADDRS_COUNT];
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};
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void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab);
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void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab);
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#endif
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#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR
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@ -555,6 +555,13 @@ bool kmem_valid_obj(void *object)
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}
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EXPORT_SYMBOL_GPL(kmem_valid_obj);
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static void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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{
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if (__kfence_obj_info(kpp, object, slab))
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return;
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__kmem_obj_info(kpp, object, slab);
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}
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/**
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* kmem_dump_obj - Print available slab provenance information
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* @object: slab object for which to find provenance information.
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@ -590,6 +597,8 @@ void kmem_dump_obj(void *object)
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pr_cont(" slab%s %s", cp, kp.kp_slab_cache->name);
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else
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pr_cont(" slab%s", cp);
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if (is_kfence_address(object))
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pr_cont(" (kfence)");
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if (kp.kp_objp)
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pr_cont(" start %px", kp.kp_objp);
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if (kp.kp_data_offset)
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@ -463,7 +463,7 @@ out:
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}
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#ifdef CONFIG_PRINTK
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void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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{
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kpp->kp_ptr = object;
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kpp->kp_slab = slab;
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@ -4312,7 +4312,7 @@ int __kmem_cache_shutdown(struct kmem_cache *s)
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}
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#ifdef CONFIG_PRINTK
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void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
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{
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void *base;
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int __maybe_unused i;
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