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decompress: drop the DDict hashset on ZSTD_DCtx_reset and ZSTD_DCtx_refDDict(NULL) #4792

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decompress: drop the DDict hashset on ZSTD_DCtx_reset and ZSTD_DCtx_refDDict(NULL) #4792

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7 changes: 7 additions & 0 deletions lib/decompress/zstd_decompress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1793,6 +1793,9 @@ size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict)
assert(!dctx->staticSize); /* Impossible: ddictSet cannot have been allocated if static dctx */
FORWARD_IF_ERROR(ZSTD_DDictHashSet_addDDict(dctx->ddictSet, ddict, dctx->customMem), "");
}
} else if (dctx->ddictSet) {
ZSTD_freeDDictHashSet(dctx->ddictSet, dctx->customMem);
dctx->ddictSet = NULL;
}
return 0;
}
Expand Down Expand Up @@ -1955,6 +1958,10 @@ size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset)
|| (reset == ZSTD_reset_session_and_parameters) ) {
RETURN_ERROR_IF(dctx->streamStage != zdss_init, stage_wrong, "");
ZSTD_clearDict(dctx);
if (dctx->ddictSet) {
ZSTD_freeDDictHashSet(dctx->ddictSet, dctx->customMem);
dctx->ddictSet = NULL;
}
ZSTD_DCtx_resetParameters(dctx);
}
return 0;
Expand Down
74 changes: 74 additions & 0 deletions tests/fuzzer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3941,6 +3941,80 @@ static int basicUnitTests(U32 const seed, double compressibility)
}
DISPLAYLEVEL(3, "OK (ASAN would report OOB write if vulnerable)\n");

DISPLAYLEVEL(3, "test%3i : DDict hashset is dropped by reset and refDDict(NULL) : ", testNb++);
{
/* After ZSTD_reset_session_and_parameters, the DCtx must not keep
* pointers to DDicts the caller has since freed. */
const char msg[] = "reset the ddict hashset, reset the ddict hashset";
char frame[256];
char out[256];
size_t frameSize;
size_t r;
ZSTD_DCtx* const dctx = ZSTD_createDCtx();
ZSTD_CCtx* const cctx2 = ZSTD_createCCtx();
char* const dictBufA = (char*)malloc(dictBufferFixedSize);
char* const dictBufB = (char*)malloc(dictBufferFixedSize);
ZSTD_CDict* cdictA = NULL;
ZSTD_DDict* ddictA = NULL;
ZSTD_DDict* ddictB = NULL;

if (!dctx || !cctx2 || !dictBufA || !dictBufB) {
DISPLAY("alloc failed\n");
goto _output_error;
}
ZSTD_memcpy(dictBufA, dictBufferFixed, dictBufferFixedSize);
ZSTD_memcpy(dictBufB, dictBufferFixed, dictBufferFixedSize);
MEM_writeLE32(dictBufA + ZSTD_FRAMEIDSIZE, 101);
MEM_writeLE32(dictBufB + ZSTD_FRAMEIDSIZE, 102);
cdictA = ZSTD_createCDict(dictBufA, dictBufferFixedSize, 1);
ddictA = ZSTD_createDDict(dictBufA, dictBufferFixedSize);
ddictB = ZSTD_createDDict(dictBufB, dictBufferFixedSize);
if (!cdictA || !ddictA || !ddictB) {
DISPLAY("dictionary creation failed\n");
goto _output_error;
}
frameSize = ZSTD_compress_usingCDict(cctx2, frame, sizeof(frame), msg, sizeof(msg), cdictA);
if (ZSTD_isError(frameSize)) goto _output_error;

CHECK_Z( ZSTD_DCtx_setParameter(dctx, ZSTD_d_refMultipleDDicts, ZSTD_rmd_refMultipleDDicts) );
CHECK_Z( ZSTD_DCtx_refDDict(dctx, ddictA) );
CHECK_Z( ZSTD_DCtx_reset(dctx, ZSTD_reset_session_and_parameters) );
ZSTD_freeDDict(ddictA);
ddictA = NULL;

/* Only ddictB is referenced now: a frame that asks for dictID 101
* must be rejected, and must not look at the freed ddictA. */
CHECK_Z( ZSTD_DCtx_setParameter(dctx, ZSTD_d_refMultipleDDicts, ZSTD_rmd_refMultipleDDicts) );
CHECK_Z( ZSTD_DCtx_refDDict(dctx, ddictB) );
r = ZSTD_decompressDCtx(dctx, out, sizeof(out), frame, frameSize);
if (!ZSTD_isError(r)) {
DISPLAY("frame decoded with a dictionary that was reset away\n");
goto _output_error;
}

/* Same thing for ZSTD_DCtx_refDDict(dctx, NULL). */
{ ZSTD_DDict* const ddictA2 = ZSTD_createDDict(dictBufA, dictBufferFixedSize);
if (!ddictA2) goto _output_error;
CHECK_Z( ZSTD_DCtx_refDDict(dctx, ddictA2) );
CHECK_Z( ZSTD_DCtx_refDDict(dctx, NULL) );
ZSTD_freeDDict(ddictA2);
CHECK_Z( ZSTD_DCtx_refDDict(dctx, ddictB) );
r = ZSTD_decompressDCtx(dctx, out, sizeof(out), frame, frameSize);
if (!ZSTD_isError(r)) {
DISPLAY("frame decoded with a dictionary that was unreferenced\n");
goto _output_error;
}
}

ZSTD_freeDDict(ddictB);
ZSTD_freeCDict(cdictA);
ZSTD_freeCCtx(cctx2);
ZSTD_freeDCtx(dctx);
free(dictBufA);
free(dictBufB);
}
DISPLAYLEVEL(3, "OK \n");

ZSTD_freeCCtx(cctx);
free(dictBuffer);
free(samplesSizes);
Expand Down