--- clamav-0.88.7.orig/libclamav/fsg.c
+++ clamav-0.88.7/libclamav/fsg.c
@@ -72,7 +72,8 @@
char *csrc = source, *cdst = dest;
int oob, lostbit = 1;
- /* I assume buffers size is >0 - No checking! */
+ if (ssize<=0 || dsize<=0) return -1;
+
*cdst++=*csrc++;
while ( 1 ) {