[PATCH] line-log: use COPY_ARRAY to fix mis-sized memcpy

[Jeff King <peff@peff.net>]

On Sun, Mar 05, 2017 at 06:36:19AM -0500, Jeff King wrote:

> >  	range_set_init(dst, src->nr);
> > -	memcpy(dst->ranges, src->ranges, src->nr*sizeof(struct range_set));
> > +	memcpy(dst->ranges, src->ranges, src->nr*sizeof(struct range));
> 
> I think "sizeof(*dst->ranges)" is probably an even better fix, as it
> infers the type of "dst". But these days we have COPY_ARRAY() to make it
> even harder to get this kind of thing wrong.

So here's your fix wrapped up with a commit message, mostly for Junio's
convenience. I listed you as the author, since you did the hard part. If
you're OK with it, please indicate that it's OK to add your
signed-off-by. If you prefer to do it differently, feel free to post
your own patch.

-- >8 --
From: Vegard Nossum <vegard.nossum@oracle.com>
Subject: [PATCH] line-log: use COPY_ARRAY to fix mis-sized memcpy

This memcpy meant to get the sizeof a "struct range", not a
"range_set", as the former is what our array holds. Rather
than swap out the types, let's convert this site to
COPY_ARRAY, which avoids the problem entirely (and confirms
that the src and dst types match).

Note for curiosity's sake that this bug doesn't trigger on
I32LP64 systems, but does on ILP32 systems. The mistaken
"struct range_set" has two ints and a pointer. That's 16
bytes on LP64, or 12 on ILP32. The correct "struct range"
type has two longs, which is also 16 on LP64, but only 8 on
ILP32.

Likewise an IL32P64 system would experience the bug.

Signed-off-by: Jeff King <peff@peff.net>
---
 line-log.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/line-log.c b/line-log.c
index 65f3558b3..a2477f601 100644
--- a/line-log.c
+++ b/line-log.c
@@ -43,9 +43,10 @@ void range_set_release(struct range_set *rs)
 static void range_set_copy(struct range_set *dst, struct range_set *src)
 {
 	range_set_init(dst, src->nr);
-	memcpy(dst->ranges, src->ranges, src->nr*sizeof(struct range_set));
+	COPY_ARRAY(dst->ranges, src->ranges, src->nr);
 	dst->nr = src->nr;
 }
+
 static void range_set_move(struct range_set *dst, struct range_set *src)
 {
 	range_set_release(dst);
-- 
2.12.0.426.g9d5d0eeae