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Merge pull request #4626 from kevinjzhang/fix-high-memory-usage

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Fix unintended high memory usage
This commit is contained in:
kevinjzhang
2026-03-17 16:16:04 -07:00
committed by GitHub
parent e56865641e cef5a5611a
commit 3ae099b48d
2 changed files with 36 additions and 1 deletions
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lib/compress/zstd_ldm.c
+5 -1
View File
@@ -152,7 +152,11 @@ void ZSTD_ldm_adjustParameters(ldmParams_t* params,
}
}
if (params->hashLog == 0) {
params->hashLog = BOUNDED(ZSTD_HASHLOG_MIN, params->windowLog - params->hashRateLog, ZSTD_HASHLOG_MAX);
if (params->windowLog <= params->hashRateLog) {
params->hashLog = ZSTD_HASHLOG_MIN;
} else {
params->hashLog = BOUNDED(ZSTD_HASHLOG_MIN, params->windowLog - params->hashRateLog, ZSTD_HASHLOG_MAX);
}
}
if (params->minMatchLength == 0) {
params->minMatchLength = LDM_MIN_MATCH_LENGTH;
tests/fuzzer.c
+31
View File
@@ -1414,6 +1414,37 @@ static int basicUnitTests(U32 const seed, double compressibility)
}
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(3, "test%3i : ldm hashRateLog > windowLog underflow check : ", testNb++);
{
/* Test that when windowLog < hashRateLog, we don't get excessive memory usage
* due to underflow in hashLog calculation (windowLog - hashRateLog). */
ZSTD_CCtx* const cctx = ZSTD_createCCtx();
size_t const size = (1U << 10); // 1 KB
size_t const dstCapacity = ZSTD_compressBound(size);
void* src = (void*)malloc(size);
void* dst = (void*)malloc(dstCapacity);
RDG_genBuffer(src, size, 0.5, 0.5, seed);
CHECK_Z(ZSTD_CCtx_setParameter(cctx, ZSTD_c_enableLongDistanceMatching, ZSTD_ps_enable));
CHECK_Z(ZSTD_CCtx_setParameter(cctx, ZSTD_c_ldmHashLog, 0));
CHECK_Z(ZSTD_CCtx_setParameter(cctx, ZSTD_c_windowLog, 12));
CHECK_Z(ZSTD_CCtx_setParameter(cctx, ZSTD_c_ldmHashRateLog, 13));
CHECK_Z(ZSTD_compress2(cctx, dst, dstCapacity, src, size));
{ size_t const cctxSize = ZSTD_sizeof_CCtx(cctx);
DISPLAYLEVEL(3, "CCtx size: %u bytes ", (unsigned)cctxSize);
CHECK_LT(cctxSize, 50 MB);
}
ZSTD_freeCCtx(cctx);
free(src);
free(dst);
}
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(3, "test%3i : testing dict compression with enableLdm and forceMaxWindow : ", testNb++);
{
ZSTD_CCtx* const cctx = ZSTD_createCCtx();