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Plug a small race in update-ref.c.

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Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Junio C Hamano 2005-09-25 16:28:51 -07:00
parent 66bf85a462
commit 152da3dfcf
1 changed files with 22 additions and 4 deletions
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26
update-ref.c
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@ -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);