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Fix noodle SVE2 off by one bug

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By using svmatch on 16 bit lanes with a 8 bit predicate, we end up
including an undefined character in the pattern checks. The inactive
lane after load contains an undefined value, usually \0. Patterns
using \0 as the last character would then match this spurious
character, returning a match beyond the buffer's end. The fix checks
for such matches and rejects them.

Signed-off-by: Yoan Picchi <yoan.picchi@arm.com>
This commit is contained in:
Yoan Picchi 2024-07-31 17:13:31 +00:00
parent b312112e87
commit 48dd0e5ff0
1 changed files with 9 additions and 2 deletions
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7
src/hwlm/noodle_engine_sve.hpp
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@ -38,8 +38,12 @@ hwlm_error_t checkMatched(const struct noodTable *n, const u8 *buf, size_t len,
size_t matchPos = basePos + svcntp_b8(svptrue_b8(), brk);
DEBUG_PRINTF("match pos %zu\n", matchPos);
assert(matchPos < len);
size_t end_of_match_pos = matchPos - cbi->offsetAdj + n->key_offset - 1;
// doubleMatched can add a fake \0 at the end of the buffer. This check get rid of any match that might include it
if(end_of_match_pos < len) {
hwlmcb_rv_t rv = final(n, buf, len, needsConfirm, cbi, matchPos);
RETURN_IF_TERMINATED(rv);
}
next_match = svpnext_b8(matched, next_match);
} while (unlikely(svptest_any(svptrue_b8(), next_match)));
return HWLM_SUCCESS;
@ -155,6 +159,9 @@ svbool_t doubleMatched(svuint16_t chars, const u8 *d,
// d - 1 won't underflow as the first position in buf has been dealt
// with meaning that d > buf
svuint16_t vec_rot = svreinterpret_u16(svld1_u8(pg_rot, d - 1));
// we reuse u8 predicates for u16 lanes. This means that we may actually check against one
// undefined extra character at the end of the buffer (usually \0). We check it later to
// reject this spurious match
*matched = svmatch(pg, vec, chars);
*matched_rot = svmatch(pg_rot, vec_rot, chars);
return svorr_z(svptrue_b8(), *matched, *matched_rot);