From 2400cc4baadc01b3f674e1b9b45ca96ebf3867c6 Mon Sep 17 00:00:00 2001
From: He Sun <bochang.sh@antfin.com>
Date: Fri, 24 Jul 2020 09:45:08 +0800
Subject: [PATCH] Fix the signal action examination of SIGKILL and SIGSTOP

Sigaction() can be called with a NULL second argument to query the
current signal handler.
---
 src/libos/src/signal/do_sigaction.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libos/src/signal/do_sigaction.rs b/src/libos/src/signal/do_sigaction.rs
index 71dc2b49..373530d4 100644
--- a/src/libos/src/signal/do_sigaction.rs
+++ b/src/libos/src/signal/do_sigaction.rs
@@ -8,7 +8,7 @@ pub fn do_rt_sigaction(signum: SigNum, new_sa: Option<SigAction>) -> Result<SigA
         &signum, &new_sa
     );
 
-    if signum == SIGKILL || signum == SIGSTOP {
+    if (signum == SIGKILL || signum == SIGSTOP) && new_sa.is_some() {
         return_errno!(
             EINVAL,
             "The actions for SIGKILL or SIGSTOP cannot be changed"