Re: [PATCH] setup_revisions(): do not access outside argv

[Jeff King <peff@peff.net>]

On Fri, May 22, 2009 at 03:56:20AM -0400, Jeff King wrote:

> Yeah, it is fine because it just passes the result to prep_temp_blob,
> which respects the length. I don't know if it is worth making it more
> safe (arguably it should just be using strbuf_readlink anyway, but that
> does introduce an extra malloc).

And here is the strbuf_readlink version, which actually does make the
source shorter and easier to read.

-- >8 --
Subject: [PATCH] convert bare readlink to strbuf_readlink

This particular readlink call never NUL-terminated its
result, making it a potential source of bugs (though there
is no bug now, as it currently always respects the length
field). Let's just switch it to strbuf_readlink which is
shorter and less error-prone.

Signed-off-by: Jeff King <peff@peff.net>
---
 diff.c |   10 +++-------
 1 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/diff.c b/diff.c
index f06876b..ffbe5c4 100644
--- a/diff.c
+++ b/diff.c
@@ -2014,14 +2014,10 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 			die("stat(%s): %s", name, strerror(errno));
 		}
 		if (S_ISLNK(st.st_mode)) {
-			int ret;
-			char buf[PATH_MAX + 1]; /* ought to be SYMLINK_MAX */
-			ret = readlink(name, buf, sizeof(buf));
-			if (ret < 0)
+			struct strbuf sb = STRBUF_INIT;
+			if (strbuf_readlink(&sb, name, st.st_size) < 0)
 				die("readlink(%s)", name);
-			if (ret == sizeof(buf))
-				die("symlink too long: %s", name);
-			prep_temp_blob(name, temp, buf, ret,
+			prep_temp_blob(name, temp, sb.buf, sb.len,
 				       (one->sha1_valid ?
 					one->sha1 : null_sha1),
 				       (one->sha1_valid ?
-- 
1.6.3.1.179.gec578.dirty