Subject: Re: [PATCH 2/2] Make hash-object more robust against malformed objects

From: Nguyen Thai Ngoc Duy <[email-masked]>
Date: Sat, 12 Feb 2011 21:47:06 +0700

On Sat, Feb 12, 2011 at 12:42:21PM +0100, Thomas Rast wrote:
> This patch makes t9350 fail under valgrind:
> 
> expecting success: 
> 
>         TAG=$(git hash-object -t tag -w tag-content) &&
>         git update-ref refs/tags/sonnenschein $TAG &&
>         git fast-export -C -C --signed-tags=strip --all > output &&
>         test $(grep -c "^tag " output) = 4 &&
>         ! grep "Unspecified Tagger" output &&
>         git fast-export -C -C --signed-tags=strip --all \
>                 --fake-missing-tagger > output &&
>         test $(grep -c "^tag " output) = 4 &&
>         grep "Unspecified Tagger" output
> 
> 
> ==2862== Invalid read of size 1
> ==2862==    at 0x4F0C34: prefixcmp (strbuf.c:9)
> ==2862==    by 0x4F4FB3: parse_tag_buffer (tag.c:109)

Nice. Does this fix it?

--8<--
diff --git a/tag.c b/tag.c
index ecf7c1e..9318ae5 100644
--- a/tag.c
+++ b/tag.c
@@ -97,7 +97,9 @@ int parse_tag_buffer(struct tag *item, const void *data, unsigned long size)
 		item->tagged = NULL;
 	}
 
-	if (prefixcmp(bufptr, "tag "))
+	if (bufptr + 5 < tail && !prefixcmp(bufptr, "tag "))
+		; 		/* good */
+	else
 		return -1;
 	bufptr += 4;
 	nl = memchr(bufptr, '\n', tail - bufptr);
@@ -106,7 +108,7 @@ int parse_tag_buffer(struct tag *item, const void *data, unsigned long size)
 	item->tag = xmemdupz(bufptr, nl - bufptr);
 	bufptr = nl + 1;
 
-	if (!prefixcmp(bufptr, "tagger "))
+	if (bufptr + 8 < tail && !prefixcmp(bufptr, "tagger "))
 		item->date = parse_tag_date(bufptr, tail);
 	else
 		item->date = 0;
--8<--
-- 
Duy