libfstream: guard against potential integer overflows

The differen compressor libraries use differnt integer types to tally
the buffer sizes. The libfstream library uses size_t, which may be
bigger than the actualy types, potentially causing an overflow if
trying to compress to much at once.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 9 insertions, 1 deletions

diff --git a/lib/fstream/compress/gzip.c b/lib/fstream/compress/gzip.c
index f604b71..e69f183 100644
--- a/lib/fstream/compress/gzip.c
+++ b/lib/fstream/compress/gzip.c
@@ -20,7 +20,15 @@ static int flush_inbuf(ostream_comp_t *base, bool finish)
 	size_t have;
 	int ret;
 
-	gzip->strm.avail_in = base->inbuf_used;
+	if (sizeof(size_t) > sizeof(uInt)) {
+		gzip->strm.avail_in = ~((uInt)0);
+
+		if ((size_t)gzip->strm.avail_in > base->inbuf_used)
+			gzip->strm.avail_in = (uInt)base->inbuf_used;
+	} else {
+		gzip->strm.avail_in = (uInt)base->inbuf_used;
+	}
+
 	gzip->strm.next_in = base->inbuf;
 
 	do {