dhcpcd: freopen of stdin/stdout may change the fd

So use dup2 instead.

diff --git a/src/dhcpcd.c b/src/dhcpcd.c
index 5de55fafc63d500e15643b03b100828f8f03b558..53d5de4421e7310f686bf1d481746a100eff70dd 100644 (file)
--- a/src/dhcpcd.c
+++ b/src/dhcpcd.c
@@ -1869,6 +1869,22 @@ dhcpcd_pidfile_timeout(void *arg)
                    dhcpcd_pidfile_timeout, ctx);
 }
 
+static int dup_null(int fd)
+{
+       int err;
+       int fd_null = open(_PATH_DEVNULL, O_RDONLY);
+
+       if (fd_null == -1) {
+               logwarn("open %s", _PATH_DEVNULL);
+               return -1;
+       }
+
+       if ((err = dup2(fd, fd_null)) == -1)
+               logwarn("dup2 %d", fd);
+       close(fd);
+       return err;
+}
+
 int
 main(int argc, char **argv, char **envp)
 {
@@ -2341,8 +2357,10 @@ printpidfile:
        }
 
        loginfox(PACKAGE "-" VERSION " starting");
-       if (ctx.stdin_valid && freopen(_PATH_DEVNULL, "w", stdin) == NULL)
-               logwarn("freopen stdin");
+
+       // We don't need stdin past this point
+       if (ctx.stdin_valid)
+               dup_null(STDIN_FILENO);
 
 #if defined(USE_SIGNALS) && !defined(THERE_IS_NO_FORK)
        if (!(ctx.options & DHCPCD_DAEMONISE))
@@ -2385,10 +2403,9 @@ printpidfile:
                                logerr("dup2");
                        close(stderr_fd[0]);
                        close(stderr_fd[1]);
-               } else if (ctx.stdout_valid) {
-                       if (freopen(_PATH_DEVNULL, "w", stdout) == NULL)
-                               logerr("freopen stdout");
-               }
+               } else if (ctx.stdout_valid)
+                       dup_null(STDOUT_FILENO);
+
                if (setsid() == -1) {
                        logerr("%s: setsid", __func__);
                        goto exit_failure;