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mdbx: fix minor zero-length memcmp() UB.

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This commit is contained in:
Leonid Yuriev 2021-08-14 17:38:37 +03:00
parent e3300259ff
commit 42d545e579
1 changed files with 14 additions and 11 deletions
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25
src/core.c
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@ -12908,25 +12908,26 @@ static int __hot cmp_int_unaligned(const MDBX_val *a, const MDBX_val *b) {
/* Compare two items lexically */ /* Compare two items lexically */
static int __hot cmp_lexical(const MDBX_val *a, const MDBX_val *b) { static int __hot cmp_lexical(const MDBX_val *a, const MDBX_val *b) {
if (a->iov_len == b->iov_len) if (a->iov_len == b->iov_len)
return memcmp(a->iov_base, b->iov_base, a->iov_len); return a->iov_len ? memcmp(a->iov_base, b->iov_base, a->iov_len) : 0;
const int diff_len = (a->iov_len < b->iov_len) ? -1 : 1; const int diff_len = (a->iov_len < b->iov_len) ? -1 : 1;
const size_t shortest = (a->iov_len < b->iov_len) ? a->iov_len : b->iov_len; const size_t shortest = (a->iov_len < b->iov_len) ? a->iov_len : b->iov_len;
int diff_data = memcmp(a->iov_base, b->iov_base, shortest); int diff_data = shortest ? memcmp(a->iov_base, b->iov_base, shortest) : 0;
return likely(diff_data) ? diff_data : diff_len; return likely(diff_data) ? diff_data : diff_len;
} }
/* Compare two items in reverse byte order */ /* Compare two items in reverse byte order */
static int __hot cmp_reverse(const MDBX_val *a, const MDBX_val *b) { static int __hot cmp_reverse(const MDBX_val *a, const MDBX_val *b) {
const uint8_t *pa = (const uint8_t *)a->iov_base + a->iov_len;
const uint8_t *pb = (const uint8_t *)b->iov_base + b->iov_len;
const size_t shortest = (a->iov_len < b->iov_len) ? a->iov_len : b->iov_len; const size_t shortest = (a->iov_len < b->iov_len) ? a->iov_len : b->iov_len;
if (likely(shortest)) {
const uint8_t *const end = pa - shortest; const uint8_t *pa = (const uint8_t *)a->iov_base + a->iov_len;
while (pa != end) { const uint8_t *pb = (const uint8_t *)b->iov_base + b->iov_len;
int diff = *--pa - *--pb; const uint8_t *const end = pa - shortest;
if (likely(diff)) do {
return diff; int diff = *--pa - *--pb;
if (likely(diff))
return diff;
} while (pa != end);
} }
return CMP2INT(a->iov_len, b->iov_len); return CMP2INT(a->iov_len, b->iov_len);
} }
@ -12934,7 +12935,9 @@ static int __hot cmp_reverse(const MDBX_val *a, const MDBX_val *b) {
/* Fast non-lexically comparator */ /* Fast non-lexically comparator */
static int __hot cmp_lenfast(const MDBX_val *a, const MDBX_val *b) { static int __hot cmp_lenfast(const MDBX_val *a, const MDBX_val *b) {
int diff = CMP2INT(a->iov_len, b->iov_len); int diff = CMP2INT(a->iov_len, b->iov_len);
return likely(diff) ? diff : memcmp(a->iov_base, b->iov_base, a->iov_len); return likely(diff || a->iov_len == 0)
? diff
: memcmp(a->iov_base, b->iov_base, a->iov_len);
} }
static bool unsure_equal(MDBX_cmp_func cmp, const MDBX_val *a, static bool unsure_equal(MDBX_cmp_func cmp, const MDBX_val *a,