Merge pull request #3937 from facebook/offset0

new method to deal with offset==0 erroneous edge case
2024-03-12 09:25:06 -07:00
parent 8ba5bc4729 eb5f7a7fa2
commit fe7c645a7e
4 changed files with 61 additions and 15 deletions
@@ -1305,7 +1305,7 @@ ZSTD_decodeSequence(seqState_t* seqState, const ZSTD_longOffset_e longOffsets, c
                } else {
                    offset = ofBase + ll0 + BIT_readBitsFast(&seqState->DStream, 1);
                    {   size_t temp = (offset==3) ? seqState->prevOffset[0] - 1 : seqState->prevOffset[offset];
-                        temp += !temp;   /* 0 is not valid; input is corrupted; force offset to 1 */
+                        temp -= !temp; /* 0 is not valid: input corrupted => force offset to -1 => corruption detected at execSequence */
                        if (offset != 1) seqState->prevOffset[2] = seqState->prevOffset[1];
                        seqState->prevOffset[1] = seqState->prevOffset[0];
                        seqState->prevOffset[0] = offset = temp;