kfence: move saving stack trace of allocations into __kfence_alloc()
Move the saving of the stack trace of allocations into __kfence_alloc(), so that the stack entries array can be used outside of kfence_guarded_alloc() and we avoid potentially unwinding the stack multiple times. Link: https://lkml.kernel.org/r/20210923104803.2620285-3-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Alexander Potapenko <glider@google.com> Cc: Aleksandr Nogikh <nogikh@google.com> Cc: Jann Horn <jannh@google.com> Cc: Taras Madan <tarasmadan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -187,19 +187,26 @@ static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *m
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* Update the object's metadata state, including updating the alloc/free stacks
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* depending on the state transition.
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*/
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static noinline void metadata_update_state(struct kfence_metadata *meta,
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enum kfence_object_state next)
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static noinline void
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metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state next,
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unsigned long *stack_entries, size_t num_stack_entries)
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{
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struct kfence_track *track =
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next == KFENCE_OBJECT_FREED ? &meta->free_track : &meta->alloc_track;
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lockdep_assert_held(&meta->lock);
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/*
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* Skip over 1 (this) functions; noinline ensures we do not accidentally
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* skip over the caller by never inlining.
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*/
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track->num_stack_entries = stack_trace_save(track->stack_entries, KFENCE_STACK_DEPTH, 1);
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if (stack_entries) {
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memcpy(track->stack_entries, stack_entries,
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num_stack_entries * sizeof(stack_entries[0]));
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} else {
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/*
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* Skip over 1 (this) functions; noinline ensures we do not
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* accidentally skip over the caller by never inlining.
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*/
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num_stack_entries = stack_trace_save(track->stack_entries, KFENCE_STACK_DEPTH, 1);
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}
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track->num_stack_entries = num_stack_entries;
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track->pid = task_pid_nr(current);
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track->cpu = raw_smp_processor_id();
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track->ts_nsec = local_clock(); /* Same source as printk timestamps. */
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@ -261,7 +268,8 @@ static __always_inline void for_each_canary(const struct kfence_metadata *meta,
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}
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}
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static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t gfp)
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static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t gfp,
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unsigned long *stack_entries, size_t num_stack_entries)
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{
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struct kfence_metadata *meta = NULL;
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unsigned long flags;
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@ -320,7 +328,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g
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addr = (void *)meta->addr;
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/* Update remaining metadata. */
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metadata_update_state(meta, KFENCE_OBJECT_ALLOCATED);
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metadata_update_state(meta, KFENCE_OBJECT_ALLOCATED, stack_entries, num_stack_entries);
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/* Pairs with READ_ONCE() in kfence_shutdown_cache(). */
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WRITE_ONCE(meta->cache, cache);
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meta->size = size;
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@ -400,7 +408,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z
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memzero_explicit(addr, meta->size);
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/* Mark the object as freed. */
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metadata_update_state(meta, KFENCE_OBJECT_FREED);
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metadata_update_state(meta, KFENCE_OBJECT_FREED, NULL, 0);
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raw_spin_unlock_irqrestore(&meta->lock, flags);
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@ -742,6 +750,9 @@ void kfence_shutdown_cache(struct kmem_cache *s)
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void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
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{
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unsigned long stack_entries[KFENCE_STACK_DEPTH];
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size_t num_stack_entries;
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/*
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* Perform size check before switching kfence_allocation_gate, so that
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* we don't disable KFENCE without making an allocation.
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@ -786,7 +797,9 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags)
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if (!READ_ONCE(kfence_enabled))
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return NULL;
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return kfence_guarded_alloc(s, size, flags);
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num_stack_entries = stack_trace_save(stack_entries, KFENCE_STACK_DEPTH, 0);
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return kfence_guarded_alloc(s, size, flags, stack_entries, num_stack_entries);
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}
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size_t kfence_ksize(const void *addr)
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