Re: [PATCH] fetch--tool: fix uninitialized buffer when reading from stdin

From

Junio C Hamano <junkio@cox.net>

Date

Feb 26, 2007, 19:37 UTC

Message-ID

<7vfy8sn20o.fsf@assigned-by-dhcp.cox.net>

In-Reply-To

<Pine.LNX.4.64.0702261003480.12485@woody.linux-foundation.org>

Linus Torvalds <torvalds@linux-foundation.org> writes:

> Well, that CHUNK_SIZE is just silly. I don't see why you'd have a 
> chunk-size of a megabyte to begin with, IO doesn't really get any more 
> efficient that way. And yeah, in this case it would easily hide the bug, 
> because in practice nobody would ever test with that much input data.
>
> It might make sense to make the chunk-size smaller just from a testability 
> standpoint (not to mention that it's probably currently just wasting 
> memory for most users - although at least under Linux, if you never use a 
> page, none will be allocated for you, so the OS may hide the wastage).

How about doing this instead?

Signed-off-by: Junio C Hamano <junkio@cox.net>
---

 builtin-fetch--tool.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/builtin-fetch--tool.c b/builtin-fetch--tool.c
index 48de08d..a068f8d 100644
--- a/builtin-fetch--tool.c
+++ b/builtin-fetch--tool.c
@@ -2,17 +2,24 @@
 #include "refs.h"
 #include "commit.h"
 
-#define CHUNK_SIZE (1048576)
+#define CHUNK_SIZE 1024
 
 static char *get_stdin(void)
 {
+	int offset = 0;
 	char *data = xmalloc(CHUNK_SIZE);
-	int offset = 0, read = 0;
-	read = xread(0, data, CHUNK_SIZE);
-	while (read == CHUNK_SIZE) {
-		offset += CHUNK_SIZE;
+
+	while (1) {
+		int cnt = xread(0, data + offset, CHUNK_SIZE);
+		if (cnt < 0)
+			die("error reading standard input: %s",
+			    strerror(errno));
+		if (cnt == 0) {
+			data[offset] = 0;
+			break;
+		}
+		offset += cnt;
 		data = xrealloc(data, offset + CHUNK_SIZE);
-		read = xread(0, data + offset, CHUNK_SIZE);
 	}
 	return data;
 }