Re: [PATCH 3/3] write_sha1_file_prepare: fix buffer overrun with extra-long object type

From: Junio C Hamano <gitster@pobox.com>
Date: May 4, 2015, 17:59 UTC
Message-ID: <xmqqzj5krzpe.fsf@gitster.dls.corp.google.com>
In-Reply-To: <xmqq4mnsteb8.fsf@gitster.dls.corp.google.com>

By the way, you would notice that "if we have returnsha1, then copy that in" bit is not in the new literally codepath but still is in write_sha1_file().

I do not think any caller passes a NULL as return_sha1 in today's code, which made me curious.

It turns out to be a remnant of d6d3f9d0 (This implements the new "recursive tree" write-tree., 2005-04-09); before that change, write_sha1_file() did not have an ability to tell the caller what object it wrote, and Linus made it optional for the callers when he added the return_sha1[] out parameter, but all of its callers did want the resulting object name.

So I think it is safe and sensible to do the following change regardless of "hash-object --literally" fix.

 sha1_file.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/sha1_file.c b/sha1_file.c
index c8ab069..96e813f 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -3002,9 +3002,8 @@ static int freshen_packed_object(const unsigned char *sha1)
 	return find_pack_entry(sha1, &e) && freshen_file(e.p->pack_name);
 }
 
-int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
+int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1)
 {
-	unsigned char sha1[20];
 	char hdr[32];
 	int hdrlen;
 
@@ -3012,8 +3011,6 @@ int write_sha1_file(const void *buf, unsigned long len, const char *type, unsign
 	 * it out into .git/objects/??/?{38} file.
 	 */
 	write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
-	if (returnsha1)
-		hashcpy(returnsha1, sha1);
 	if (freshen_loose_object(sha1) || freshen_packed_object(sha1))
 		return 0;
 	return write_loose_object(sha1, hdr, hdrlen, buf, len, 0);