Fix heap corruption from too small kbloom #213
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kbloom is a bitmask with 'size2' bits, where 'size2' is the next power of 2 of 'size'. Thus, if 'size' is smaller than 4, 'size2' is smaller than 8, so that size2 / 8 == 0 and calloc allocates 0 bytes. This causes heap corruption when kbloom is subsequently written to. See discussion on https://groups.google.com/g/librsync/c/vmqzQS1QjIw.
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Note that the Bloom filter only helps if the hashtable is larger than L1 cache, which is about 8K entries. We could also just not allocate a bloom filter at all if the hash table is small and change the bloom filter setting/checking to do nothing if t->kbloom is NULL. However, this is a much simpler fix for now, so I'm going to merge it. |
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kbloom is a bitmask with 'size2' bits, where 'size2' is the next power of 2 of 'size'. Thus, if 'size' is smaller than 4, 'size2' is smaller than 8, so that size2 / 8 == 0 and calloc allocates 0 bytes. This causes heap corruption when kbloom is subsequently written to. See discussion on https://groups.google.com/g/librsync/c/vmqzQS1QjIw.