Subject: Suspicious code in builtin-fast-export.c

From: Johannes Sixt <[email-masked]>
Date: Wed, 02 Jul 2008 11:04:28 +0200

export_marks() has this code:

	struct object_decoration *deco = idnums.hash;
...
	for (i = 0; i < idnums.size; ++i) {
		deco++;
		if (deco && deco->base && deco->base->type == 1) {
...
		}
	}

I see that deco is off by one here at the end of the idnums.hash array
(and, btw, the check for 'deco &&' is always true). Indeed, this crashes
on Windows, and I can make it crash on Linux with this patch (which
overallocates a bit and writes junk into that space):

diff --git a/wrapper.c b/wrapper.c
index 4e04f76..658925e 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -72,7 +72,7 @@ void *xrealloc(void *ptr, size_t size)

 void *xcalloc(size_t nmemb, size_t size)
 {
-	void *ret = calloc(nmemb, size);
+	void *ret = calloc(nmemb+1, size);
 	if (!ret && (!nmemb || !size))
 		ret = calloc(1, 1);
 	if (!ret) {
@@ -83,6 +83,7 @@ void *xcalloc(size_t nmemb, size_t size)
 		if (!ret)
 			die("Out of memory, calloc failed");
 	}
+	memset(ret+nmemb*size, 0xDE, size);
 	return ret;
 }

-- 
1.5.6.64.gd77fe