apply: reallocate the postimage buffer when neededcn/apply-fix-ws-can-lengthen-lines

The buffer in the postimage may become too small when whitespace fixes
are applied to the patch and update_pre_post_images might write past
the end of the buffer.

Teach the code to reallocate the buffer if needed. When it comes time
to free the buffer, do it directly on postimage.buf instead of the
newlines strbuf.

Signed-off-by: Carlos Martín Nieto <cmn@elego.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/builtin/apply.c b/builtin/apply.c
index 389898f133..8899b09c2e 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -2003,10 +2003,12 @@ static void update_pre_post_images(struct image *preimage,
 	 * in place (postlen==0) or not.
 	 */
 	old = postimage->buf;
-	if (postlen)
+	if (postlen) {
 		new = postimage->buf = xmalloc(postlen);
-	else
+		postimage->alloc = postlen;
+	} else {
 		new = old;
+	}
 	fixed = preimage->buf;
 	for (i = ctx = 0; i < postimage->nr; i++) {
 		size_t len = postimage->line[i].len;
@@ -2032,6 +2034,13 @@ static void update_pre_post_images(struct image *preimage,
 
 		/* and copy it in, while fixing the line length */
 		len = preimage->line[ctx].len;
+		if (postimage->alloc < (new - postimage->buf) + len) {
+			size_t post_len = new - postimage->buf;
+			postimage->buf = xrealloc(postimage->buf, post_len + len);
+			postimage->alloc = post_len + len;
+			new = postimage->buf + post_len;
+		}
+
 		memcpy(new, fixed, len);
 		new += len;
 		fixed += len;
@@ -2594,6 +2603,7 @@ static int apply_one_fragment(struct image *img, struct fragment *frag,
 	preimage.len = old - oldlines;
 	postimage.buf = newlines.buf;
 	postimage.len = newlines.len;
+	postimage.alloc = newlines.alloc;
 	preimage.line = preimage.line_allocated;
 	postimage.line = postimage.line_allocated;
 
@@ -2679,7 +2689,7 @@ static int apply_one_fragment(struct image *img, struct fragment *frag,
 	}
 
 	free(oldlines);
-	strbuf_release(&newlines);
+	free(postimage.buf);
 	free(preimage.line_allocated);
 	free(postimage.line_allocated);