kfence: move the size check to the beginning of __kfence_alloc()
Check the allocation size before toggling kfence_allocation_gate. This way allocations that can't be served by KFENCE will not result in waiting for another CONFIG_KFENCE_SAMPLE_INTERVAL without allocating anything. Link: https://lkml.kernel.org/r/20210714092222.1890268-1-glider@google.com Signed-off-by: Alexander Potapenko <glider@google.com> Suggested-by: Marco Elver <elver@google.com> Reviewed-by: Marco Elver <elver@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Marco Elver <elver@google.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <stable@vger.kernel.org> [5.12+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -733,6 +733,13 @@ 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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/*
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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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*/
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if (size > PAGE_SIZE)
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return NULL;
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/*
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* allocation_gate only needs to become non-zero, so it doesn't make
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* sense to continue writing to it and pay the associated contention
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@ -757,9 +764,6 @@ 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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if (size > PAGE_SIZE)
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return NULL;
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return kfence_guarded_alloc(s, size, flags);
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}
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