[lxc-devel] [lxc/master] avoid a NULL pointer dereference in lxc-attach

[alliedtelesis on Github]

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From d9346e19eb953c9f71d545019fc260da046e910f Mon Sep 17 00:00:00 2001
From: Scott Parlane <scott.parlane at alliedtelesis.co.nz>
Date: Wed, 2 Sep 2020 17:01:11 +1200
Subject: [PATCH] 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 at alliedtelesis.co.nz>
---
 src/lxc/attach.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index 4b95989227..368dd41ad1 100644
--- 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,
-					      &terminal.tty_state->oldmask, NULL);
-			if (ret < 0) {
-				SYSERROR("Failed to reset signal mask");
-				_exit(EXIT_FAILURE);
+			if (terminal.tty_state)
+			{
+				ret = pthread_sigmask(SIG_SETMASK,
+							  &terminal.tty_state->oldmask, NULL);
+				if (ret < 0) {
+					SYSERROR("Failed to reset signal mask");
+					_exit(EXIT_FAILURE);
+				}
 			}
 		}