terminal: prevent returning invalid pointer

Closes: https://github.com/lxc/lxd/issues/6408
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/terminal.c b/src/lxc/terminal.c
index 31186972a077e0aafe1b524f4eb147e19eecaa42..18769b794b6cbd1e1805e25637cc8f66ab117c28 100644 (file)
--- a/src/lxc/terminal.c
+++ b/src/lxc/terminal.c
@@ -115,8 +115,8 @@ int lxc_terminal_signalfd_cb(int fd, uint32_t events, void *cbdata,
 
 struct lxc_terminal_state *lxc_terminal_signal_init(int srcfd, int dstfd)
 {
+       __do_close_prot_errno int signal_fd = -EBADF;
        __do_free struct lxc_terminal_state *ts = NULL;
-       bool istty = false;
        int ret;
        sigset_t mask;
 
@@ -132,49 +132,40 @@ struct lxc_terminal_state *lxc_terminal_signal_init(int srcfd, int dstfd)
        ret = sigemptyset(&mask);
        if (ret < 0) {
                SYSERROR("Failed to initialize an empty signal set");
-               goto on_error;
+               return NULL;
        }
 
-       istty = (isatty(srcfd) == 1);
-       if (!istty) {
-               INFO("fd %d does not refer to a tty device", srcfd);
-       } else {
+       if (isatty(srcfd)) {
                ret = sigaddset(&mask, SIGWINCH);
                if (ret < 0)
                        SYSNOTICE("Failed to add SIGWINCH to signal set");
+       } else {
+               INFO("fd %d does not refer to a tty device", srcfd);
        }
 
        /* Exit the mainloop cleanly on SIGTERM. */
        ret = sigaddset(&mask, SIGTERM);
        if (ret < 0) {
                SYSERROR("Failed to add SIGWINCH to signal set");
-               goto on_error;
+               return NULL;
        }
 
        ret = pthread_sigmask(SIG_BLOCK, &mask, &ts->oldmask);
        if (ret < 0) {
                WARN("Failed to block signals");
-               goto on_error;
+               return NULL;
        }
 
-       ts->sigfd = signalfd(-1, &mask, SFD_CLOEXEC);
-       if (ts->sigfd < 0) {
+       signal_fd = signalfd(-1, &mask, SFD_CLOEXEC);
+       if (signal_fd < 0) {
                WARN("Failed to create signal fd");
                (void)pthread_sigmask(SIG_SETMASK, &ts->oldmask, NULL);
-               goto on_error;
-       }
-
-       DEBUG("Created signal fd %d", ts->sigfd);
-       return ts;
-
-on_error:
-       ERROR("Failed to create signal fd");
-       if (ts->sigfd >= 0) {
-               close(ts->sigfd);
-               ts->sigfd = -1;
+               return NULL;
        }
+       ts->sigfd = move_fd(signal_fd);
+       TRACE("Created signal fd %d", ts->sigfd);
 
-       return NULL;
+       return move_ptr(ts);
 }
 
 /**