Subject: Re: [PATCH] Fix delta integer overflows

From: Martin Koegler <[email-masked]>
Date: Tue, 8 Aug 2017 08:20:47 +0200

On Mon, Aug 07, 2017 at 09:39:12PM +0200, Johannes Schindelin wrote:
> If you want to work on data in memory, then size_t is the appropriate data
> type. We already use it elsewhere. Let's use it here, too, without the
> intermediate bump from the incorrect `int` to the equally incorrect
> `long`.

I disagree with "We already use it elsewhere.". The whole delta code uses "unsigned long" -
look at delta.h. Look at unpack-objects.c. Or cache.h. Or pack-objects.c. Or index-pack.c.

Other possible cases:
git grep "unsigned long" |grep size

So the codebase still suggests, that "unsigned long" is the data type for storing object sizes.

I would be fine with resubmitting a patch using size_t/off_t for the touched parts - changing the whole
core code is a too invasive change for a bug fix.

Regards,
Martin
>From d97a7810ff679dd939972c151bcf23c122cdc570 Mon Sep 17 00:00:00 2001
From: Martin Koegler <[email-masked]>
Date: Mon, 7 Aug 2017 20:00:30 +0200
Subject: [PATCH] Fix delta integer overflows

The current delta code produces incorrect pack objects for files > 4GB.

Signed-off-by: Martin Koegler <[email-masked]>
---
 diff-delta.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/diff-delta.c b/diff-delta.c
index 3797ce6..cd238c8 100644
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -319,7 +319,9 @@ create_delta(const struct delta_index *index,
 	     const void *trg_buf, unsigned long trg_size,
 	     unsigned long *delta_size, unsigned long max_size)
 {
-	unsigned int i, outpos, outsize, moff, msize, val;
+	unsigned int i, val;
+	off_t outpos, moff;
+	size_t l, outsize, msize;
 	int inscnt;
 	const unsigned char *ref_data, *ref_top, *data, *top;
 	unsigned char *out;
@@ -336,20 +338,20 @@ create_delta(const struct delta_index *index,
 		return NULL;
 
 	/* store reference buffer size */
-	i = index->src_size;
-	while (i >= 0x80) {
-		out[outpos++] = i | 0x80;
-		i >>= 7;
+	l = index->src_size;
+	while (l >= 0x80) {
+		out[outpos++] = l | 0x80;
+		l >>= 7;
 	}
-	out[outpos++] = i;
+	out[outpos++] = l;
 
 	/* store target buffer size */
-	i = trg_size;
-	while (i >= 0x80) {
-		out[outpos++] = i | 0x80;
-		i >>= 7;
+	l = trg_size;
+	while (l >= 0x80) {
+		out[outpos++] = l | 0x80;
+		l >>= 7;
 	}
-	out[outpos++] = i;
+	out[outpos++] = l;
 
 	ref_data = index->src_buf;
 	ref_top = ref_data + index->src_size;
-- 
2.1.4