avoid link during locking -- the target follows slinks,

which allows you to create random empty files as root

SCCS-vsn: libexec/mail.local/mail.local.c 8.12

diff --git a/usr/src/libexec/mail.local/mail.local.c b/usr/src/libexec/mail.local/mail.local.c
index efdd63f..9694bc2 100644 (file)
--- a/usr/src/libexec/mail.local/mail.local.c
+++ b/usr/src/libexec/mail.local/mail.local.c
@@ -12,7 +12,7 @@ static char copyright[] =
 #endif /* not lint */
 
 #ifndef lint
 #endif /* not lint */
 
 #ifndef lint

-static char sccsid[] = "@(#)mail.local.c       8.11 (Berkeley) %G%";
+static char sccsid[] = "@(#)mail.local.c       8.12 (Berkeley) %G%";

 #endif /* not lint */
 
 #include <sys/param.h>
 #endif /* not lint */
 
 #include <sys/param.h>


@@ -361,30 +361,22 @@ int       locked = 0;
 lockmbox(path)
        char *path;
 {
 lockmbox(path)
        char *path;
 {

-       char locktmp[50];

        int statfailed = 0;
 
        if (locked)
                return;
        sprintf(lockname, "%s.lock", path);
        int statfailed = 0;
 
        if (locked)
                return;
        sprintf(lockname, "%s.lock", path);

-       sprintf(locktmp, "%s/tmXXXXXX", _PATH_MAILDIR);
-       mktemp(locktmp);
-       unlink(locktmp);

        for (;; sleep(5)) {
                int fd;
                struct stat st;
                time_t now;
 
        for (;; sleep(5)) {
                int fd;
                struct stat st;
                time_t now;
 

-               fd = open(locktmp, O_WRONLY|O_EXCL|O_CREAT, 0);
-               if (fd < 0)
-                       continue;
-               close(fd);
-               if (link(locktmp, lockname) >= 0) {
-                       unlink(locktmp);
+               fd = open(lockname, O_WRONLY|O_EXCL|O_CREAT, 0);
+               if (fd >= 0) {

                        locked = 1;
                        locked = 1;

+                       close(fd);

                        return;
                }
                        return;
                }

-               unlink(locktmp);

                if (stat(lockname, &st) < 0) {
                        if (statfailed++ > 5)
                                return;
                if (stat(lockname, &st) < 0) {
                        if (statfailed++ > 5)
                                return;