Messages in this thread | | | Date | Wed, 21 Sep 2022 07:43:17 -0400 | Subject | Re: [PATCH 4/4] fortify: Use __builtin_dynamic_object_size() when available | From | Siddhesh Poyarekar <> |
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On 2022-09-20 15:22, Kees Cook wrote: > Since the commits starting with c37495d6254c ("slab: add __alloc_size > attributes for better bounds checking"), the compilers have runtime > allocation size hints available in some places. This was immediately > available to CONFIG_UBSAN_BOUNDS, but CONFIG_FORTIFY_SOURCE needed > updating to explicitly make use the hints via the associated > __builtin_dynamic_object_size() helper. Detect and use the builtin when > it is available, increasing the accuracy of the mitigation. When runtime > sizes are not available, __builtin_dynamic_object_size() falls back to > __builtin_object_size(), leaving the existing bounds checking unchanged.
I don't know yet what the overhead is for __builtin_dynamic_object_size vs __builtin_object_size, were you able to measure it somehow for the kernel? If there's a significant tradeoff, it may make sense to provide a user override.
Thanks, Sid
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