Re: [PATCH] libselinux-3

On Fri, 2003-10-24 at 15:08, Bastian Blank wrote:
> updated patch.

@@ -366,13 +366,13 @@

 	if (!ptr)
 		return -1;
 	plen = strlen(ptr);
-	if (buf[plen-1] == '\n') 
+	if (plen > 1 && buf[plen-1] == '\n') 
 		buf[plen-1] = 0;

I believe that the original code is correct, and that the patch introduces a minor bug. If the file is empty, ptr will be NULL and the !ptr test will catch it. Hence, plen should always be at least 1. Further, your test for plen > 0 means that you won't clear the newline in the case where the file contains only a newline and nothing else, i.e. plen == 1 and buf[0] == '\n'.

@@ -23,11 +23,11 @@

 	if (ret < 0 && errno == ERANGE) {
 		char *newbuf;
 
-		size = fgetxattr(fd, XATTR_NAME_SELINUX, NULL, 0);
-		if (size < 0)
+		ret = fgetxattr(fd, XATTR_NAME_SELINUX, NULL, 0);
+		if (ret < 0)
 			goto out;
 
-		size++;
+		size = ret + 1;
 		newbuf = realloc(buf, size);
 		if (!newbuf)
 			goto out;

As with the earlier patch for the *getfilecon functions, this one introduces a bug. Look at the result of this patch when the realloc fails; since ret is reset by your change, the out path will not treat it as an error, and the caller will be returned garbage without any indication that the call actually failed.

-- 
Stephen Smalley <sds@epoch.ncsc.mil>
National Security Agency


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