avoid a NULL pointer dereference in lxc-attach

Seems to appear when stderr is a terminal and not stdin or stdout. Signed-off-by: Scott Parlane <scott.parlane@alliedtelesis.co.nz>

avoid a NULL pointer dereference in lxc-attach
a836df04 · Scott Parlane · Christian Brauner · 8c23afc3 · a836df04
Unverified Commit a836df04 authored Sep 02, 2020 by Scott Parlane Committed by Christian Brauner Oct 19, 2020
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Showing with 8 additions and 5 deletions

attach.c src/lxc/attach.c +8 -5

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--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -1384,11 +1384,14 @@ int lxc_attach(struct lxc_container *container, lxc_attach_exec_t exec_function,
 	if (pid == 0) {
 		if (options->attach_flags & LXC_ATTACH_TERMINAL) {
-			ret = pthread_sigmask(SIG_SETMASK,
+			if (terminal.tty_state)
-					      &terminal.tty_state->oldmask, NULL);
+			{
-			if (ret < 0) {
+				ret = pthread_sigmask(SIG_SETMASK,
-				SYSERROR("Failed to reset signal mask");
+							  &terminal.tty_state->oldmask, NULL);
-				_exit(EXIT_FAILURE);
+				if (ret < 0) {
+					SYSERROR("Failed to reset signal mask");
+					_exit(EXIT_FAILURE);
+				}
 			}
 		}