Clarify that mspack_system.free() should accept and ignore NULL

libmspack/ChangeLog

@@ -1,3 +1,11 @@
+2018-08-13  Stuart Caie <kyzer@cabextract.org.uk>
+
+	* mspack.h: clarify that mspack_system.free() should allow NULL. If your
+	mspack_system implementation doesn't, it would already have crashed, as
+	there are several places where libmspack calls sys->free(NULL). This
+	change makes it official, and amends a few "if (x) sys->free(x)" cases
+	to the simpler "sys->free(x)" to make it clearer.
+
 2018-08-09  Stuart Caie <kyzer@cabextract.org.uk>
 
 	* Makefile.am: the test file cve-2015-4467-reset-interval-zero.chm is

libmspack/mspack/kwajd.c

@@ -113,8 +113,8 @@ static struct mskwajd_header *kwajd_open(struct mskwaj_decompressor *base,
     }
 
     if (self->error) {
-	if (fh)  sys->close(fh);
-	if (hdr) sys->free(hdr);
+	if (fh) sys->close(fh);
+	sys->free(hdr);
 	hdr = NULL;
     }
 

libmspack/mspack/mspack.h

@@ -424,7 +424,7 @@ struct mspack_system {
   /**
    * Frees memory.
    * 
-   * @param ptr the memory to be freed.
+   * @param ptr the memory to be freed. NULL is accepted and ignored.
    * @see alloc()
    */
   void (*free)(void *ptr);

libmspack/mspack/oabd.c

@@ -236,14 +236,10 @@ static int oabd_decompress(struct msoab_decompressor *_self, const char *input,
   }
 
  out:
-  if (lzx)
-    lzxd_free(lzx);
-  if (buf)
-    sys->free(buf);
-  if (outfh)
-    sys->close(outfh);
-  if (infh)
-    sys->close(infh);
+  if (lzx) lzxd_free(lzx);
+  if (outfh) sys->close(outfh);
+  if (infh) sys->close(infh);
+  sys->free(buf);
 
   return ret;
 }
@@ -390,16 +386,11 @@ static int oabd_decompress_incremental(struct msoab_decompressor *_self,
   }
 
  out:
-  if (lzx)
-    lzxd_free(lzx);
-  if (buf)
-    sys->free(buf);
-  if (outfh)
-    sys->close(outfh);
-  if (basefh)
-    sys->close(basefh);
-  if (infh)
-    sys->close(infh);
+  if (lzx) lzxd_free(lzx);
+  if (outfh) sys->close(outfh);
+  if (basefh) sys->close(basefh);
+  if (infh) sys->close(infh);
+  sys->free(buf);
 
   return ret;
 }

libmspack/mspack/szddd.c

@@ -99,8 +99,8 @@ static struct msszddd_header *szddd_open(struct msszdd_decompressor *base,
     }
 
     if (self->error) {
-	if (fh)  sys->close(fh);
-	if (hdr) sys->free(hdr);
+	if (fh) sys->close(fh);
+	sys->free(hdr);
 	hdr = NULL;
     }