From 152da3dfcf2c16d7c240a0dbdcb8a3ae1d332d81 Mon Sep 17 00:00:00 2001
From: Junio C Hamano <junkio@cox.net>
Date: Sun, 25 Sep 2005 16:28:51 -0700
Subject: [PATCH] Plug a small race in update-ref.c.
Signed-off-by: Junio C Hamano <junkio@cox.net>
---
update-ref.c | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)
diff --git a/update-ref.c b/update-ref.c
index 127ef99eed..01496f6a92 100644
--- a/update-ref.c
+++ b/update-ref.c
@@ -1,5 +1,6 @@
#include "cache.h"
#include "refs.h"
+#include <ctype.h>
static const char git_update_ref_usage[] = "git-update-ref <refname> <value> [<oldval>]";
@@ -50,6 +51,19 @@ const char *resolve_ref(const char *path, unsigned char *sha1)
return path;
}
+static int re_verify(const char *path, unsigned char *oldsha1, unsigned char *currsha1)
+{
+ char buf[40];
+ int fd = open(path, O_RDONLY), nr;
+ if (fd < 0)
+ return -1;
+ nr = read(fd, buf, 40);
+ close(fd);
+ if (nr != 40 || get_sha1_hex(buf, currsha1) < 0)
+ return -1;
+ return memcmp(oldsha1, currsha1, 20) ? -1 : 0;
+}
+
int main(int argc, char **argv)
{
char *hex;
@@ -97,12 +111,16 @@ int main(int argc, char **argv)
}
/*
- * FIXME!
- *
- * We should re-read the old ref here, and re-verify that it
- * matches "oldsha1". Otherwise there's a small race.
+ * Re-read the ref after getting the lock to verify
*/
+ if (oldval && re_verify(path, oldsha1, currsha1) < 0) {
+ unlink(lockpath);
+ die("Ref lock failed");
+ }
+ /*
+ * Finally, replace the old ref with the new one
+ */
if (rename(lockpath, path) < 0) {
unlink(lockpath);
die("Unable to create %s", path);
--
2.40.0