From 6bc7175f315bd4e2c334d60ee3364cbff63574f1 Mon Sep 17 00:00:00 2001
From: Jilles Tjoelker <jilles@FreeBSD.org>
Date: Sat, 16 May 2020 16:29:23 +0000
Subject: [PATCH] sh: Fix double INTON with vfork

The shell maintains a count of the number of times SIGINT processing has
been disabled via INTOFF, so SIGINT processing resumes when all disables
have enabled again (INTON).

If an error occurs in a vfork() child, the processing of the error enables
SIGINT processing again, and the INTON in vforkexecshell() causes the count
to become negative.

As a result, a later INTOFF may not actually disable SIGINT processing. This
might cause memory corruption if a SIGINT arrives at an inopportune time. As
of r360452, it causes the shell to abort when it would unsafely allocate or
free memory in certain ways.

Note that various places such as errors in non-special builtins
unconditionally reset the count to 0, so the problem might still not always
be visible.

PR:		246497
Reported by:	jbeich
MFC after:	2 weeks
---
 bin/sh/jobs.c                     | 4 +++-
 bin/sh/tests/execution/Makefile   | 1 +
 bin/sh/tests/execution/unknown2.0 | 6 ++++++
 3 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 bin/sh/tests/execution/unknown2.0

diff --git a/bin/sh/jobs.c b/bin/sh/jobs.c
index 2475787c1da9..c46e526eab67 100644
--- a/bin/sh/jobs.c
+++ b/bin/sh/jobs.c
@@ -1008,9 +1008,11 @@ vforkexecshell(struct job *jp, char **argv, char **envp, const char *path, int i
 	pid_t pid;
 	struct jmploc jmploc;
 	struct jmploc *savehandler;
+	int inton;
 
 	TRACE(("vforkexecshell(%%%td, %s, %p) called\n", jp - jobtab, argv[0],
 	    (void *)pip));
+	inton = is_int_on();
 	INTOFF;
 	flushall();
 	savehandler = handler;
@@ -1045,7 +1047,7 @@ vforkexecshell(struct job *jp, char **argv, char **envp, const char *path, int i
 		setcurjob(jp);
 #endif
 	}
-	INTON;
+	SETINTON(inton);
 	TRACE(("In parent shell:  child = %d\n", (int)pid));
 	return pid;
 }
diff --git a/bin/sh/tests/execution/Makefile b/bin/sh/tests/execution/Makefile
index 983db692faff..526541d50994 100644
--- a/bin/sh/tests/execution/Makefile
+++ b/bin/sh/tests/execution/Makefile
@@ -64,6 +64,7 @@ ${PACKAGE}FILES+=		subshell2.0
 ${PACKAGE}FILES+=		subshell3.0
 ${PACKAGE}FILES+=		subshell4.0
 ${PACKAGE}FILES+=		unknown1.0
+${PACKAGE}FILES+=		unknown2.0
 ${PACKAGE}FILES+=		var-assign1.0
 
 .include <bsd.test.mk>
diff --git a/bin/sh/tests/execution/unknown2.0 b/bin/sh/tests/execution/unknown2.0
new file mode 100644
index 000000000000..d316e01949f6
--- /dev/null
+++ b/bin/sh/tests/execution/unknown2.0
@@ -0,0 +1,6 @@
+# $FreeBSD$
+
+{
+	: $(/var/empty/nosuchtool) 
+	: $(:)
+} 2>/dev/null