Add a forward progress requirement bound to seekable streaming decompression
diff --git a/contrib/seekable_format/zstdseek_decompress.c b/contrib/seekable_format/zstdseek_decompress.c
index abfd1e9..eb9fd71 100644
--- a/contrib/seekable_format/zstdseek_decompress.c
+++ b/contrib/seekable_format/zstdseek_decompress.c
@@ -79,6 +79,8 @@
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#define ZSTD_SEEKABLE_NO_OUTPUT_PROGRESS_MAX 16
+
/* Special-case callbacks for FILE* and in-memory modes, so that we can treat
* them the same way as the advanced API */
static int ZSTD_seekable_read_FILE(void* opaque, void* buffer, size_t n)
@@ -380,6 +382,7 @@
size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsigned long long offset)
{
U32 targetFrame = ZSTD_seekable_offsetToFrameIndex(zs, offset);
+ U32 noOutputProgressCount = 0;
do {
/* check if we can continue from a previous decompress job */
if (targetFrame != zs->curFrame || offset != zs->decompressedOffset) {
@@ -398,6 +401,7 @@
size_t toRead;
ZSTD_outBuffer outTmp;
size_t prevOutPos;
+ size_t forwardProgress;
if (zs->decompressedOffset < offset) {
/* dummy decompressions until we get to the target offset */
outTmp = (ZSTD_outBuffer){zs->outBuff, MIN(SEEKABLE_BUFF_SIZE, offset - zs->decompressedOffset), 0};
@@ -415,7 +419,13 @@
XXH64_update(&zs->xxhState, (BYTE*)outTmp.dst + prevOutPos,
outTmp.pos - prevOutPos);
}
- zs->decompressedOffset += outTmp.pos - prevOutPos;
+ forwardProgress = outTmp.pos - prevOutPos;
+ if (!forwardProgress && noOutputProgressCount++ > ZSTD_SEEKABLE_NO_OUTPUT_PROGRESS_MAX) {
+ return ERROR(seekableIO);
+ } else {
+ noOutputProgressCount = 0;
+ }
+ zs->decompressedOffset += forwardProgress;
if (toRead == 0) {
/* frame complete */