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packfile.c: use checked arithmetic in nth_packed_object_offset()
In a similar spirit as the previous commits, ensure that we use `st_add()` or `st_mult()` when computing values that may overflow the 32-bit unsigned limit. Note that in each of these instances, we prevent 32-bit overflow already since we have explicit casts to `size_t`. So this code is OK as-is, but let's clarify it by using the `st_xyz()` helpers to make it obvious that we are performing the relevant computations using 64 bits. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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1 changed files with 5 additions and 4 deletions
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@ -1948,14 +1948,15 @@ off_t nth_packed_object_offset(const struct packed_git *p, uint32_t n)
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const unsigned int hashsz = the_hash_algo->rawsz;
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index += 4 * 256;
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if (p->index_version == 1) {
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return ntohl(*((uint32_t *)(index + (hashsz + 4) * (size_t)n)));
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return ntohl(*((uint32_t *)(index + st_mult(hashsz + 4, n))));
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} else {
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uint32_t off;
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index += 8 + (size_t)p->num_objects * (hashsz + 4);
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off = ntohl(*((uint32_t *)(index + 4 * n)));
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index += st_add(8, st_mult(p->num_objects, hashsz + 4));
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off = ntohl(*((uint32_t *)(index + st_mult(4, n))));
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if (!(off & 0x80000000))
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return off;
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index += (size_t)p->num_objects * 4 + (off & 0x7fffffff) * 8;
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index += st_add(st_mult(p->num_objects, 4),
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st_mult(off & 0x7fffffff, 8));
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check_pack_index_ptr(p, index);
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return get_be64(index);
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}
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