su: (pty) fix child signal mask usage

The signal mask is used by pty_init_slave(), but it has never been
uninitialized before fork(), so child gets 0 as a mask :-(

Note that script(1) has no this issue because it opens signal-fd
before fork().

Reported-by: Vaclav Dolezal <vdolezal@redhat.com>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/login-utils/su-common.c b/login-utils/su-common.c
index 520ecb34218a8875bd5d460cf1a35705b6a7f192..bfccb4643e446537d17b06a836848ff616eed57c 100644 (file)
--- a/login-utils/su-common.c
+++ b/login-utils/su-common.c
@@ -135,7 +135,6 @@ struct su_context {
        pid_t           child;                  /* fork() baby */
 
        struct sigaction oldact[SIGNALS_IDX_COUNT];     /* original sigactions indexed by SIG*_IDX */
-       sigset_t        oldsig;                 /* original signal mask */
 
 #ifdef USE_PTY
        struct termios  stdin_attrs;            /* stdin and slave terminal runtime attributes */
@@ -144,6 +143,7 @@ struct su_context {
        int             pty_sigfd;              /* signalfd() */
        int             poll_timeout;
        struct winsize  win;                    /* terminal window size */
+       sigset_t        oldsig;                 /* original signal mask */
 #endif
        unsigned int runuser :1,                /* flase=su, true=runuser */
                     runuser_uopt :1,           /* runuser -u specified */
@@ -460,7 +460,7 @@ static void pty_proxy_master(struct su_context *su)
         * TODO: script(1) initializes this FD before fork, good or bad idea?
         */
        sigfillset(&ourset);
-       if (sigprocmask(SIG_BLOCK, &ourset, &su->oldsig)) {
+       if (sigprocmask(SIG_BLOCK, &ourset, NULL)) {
                warn(_("cannot block signals"));
                caught_signal = true;
                return;
@@ -735,7 +735,7 @@ static void parent_setup_signals(struct su_context *su)
        DBG(SIG, ul_debug("initialize signals"));
 
        sigfillset(&ourset);
-       if (sigprocmask(SIG_BLOCK, &ourset, &su->oldsig)) {
+       if (sigprocmask(SIG_BLOCK, &ourset, NULL)) {
                warn(_("cannot block signals"));
                caught_signal = true;
        }
@@ -800,6 +800,9 @@ static void create_watching_parent(struct su_context *su)
 
        DBG(MISC, ul_debug("forking..."));
 #ifdef USE_PTY
+       /* no-op, just save original signal mask to oldsig */
+       sigprocmask(SIG_BLOCK, NULL, &su->oldsig);
+
        if (su->pty)
                pty_create(su);
 #endif