svn commit: r314686 - in head/bin/sh: . tests/expansion

[Jilles Tjoelker]

Author: jilles
Date: Sat Mar  4 22:58:34 2017
New Revision: 314686
URL: https://svnweb.freebsd.org/changeset/base/314686

Log:
  sh: Fix crash if a -T trap is taken during command substitution.
  
  Code like  t=$(stat -f %m "$file")  segfaulted if -T was active and a trap
  was taken while the shell was waiting for the child process to finish.
  
  What happened was that the dotrap() call in waitforjob() was hit. This
  re-entered command execution (including expand.c) at a point not expected by
  expbackq(), and global state (unallocated stack string and argbackq) was
  corrupted.
  
  To fix this, change expbackq() to prepare for command execution to be
  re-entered.
  
  Reported by:	bdrewery
  MFC after:	1 week

Added:
  head/bin/sh/tests/expansion/cmdsubst21.0   (contents, props changed)
  head/bin/sh/tests/expansion/cmdsubst22.0   (contents, props changed)
Modified:
  head/bin/sh/expand.c
  head/bin/sh/tests/expansion/Makefile

Modified: head/bin/sh/expand.c
==============================================================================
--- head/bin/sh/expand.c	Sat Mar  4 22:38:10 2017	(r314685)
+++ head/bin/sh/expand.c	Sat Mar  4 22:58:34 2017	(r314686)
@@ -460,7 +460,6 @@ expbackq(union node *cmd, int quoted, in
 	p = grabstackstr(dest);
 	evalbackcmd(cmd, &in);
 	ungrabstackstr(p, dest);
-	argbackq = saveargbackq;
 
 	p = in.buf;
 	nnl = 0;
@@ -514,12 +513,16 @@ expbackq(union node *cmd, int quoted, in
 		close(in.fd);
 	if (in.buf)
 		ckfree(in.buf);
-	if (in.jp)
+	if (in.jp) {
+		p = grabstackstr(dest);
 		exitstatus = waitforjob(in.jp, (int *)NULL);
+		ungrabstackstr(p, dest);
+	}
 	TRACE(("expbackq: size=%td: \"%.*s\"\n",
 		((dest - stackblock()) - startloc),
 		(int)((dest - stackblock()) - startloc),
 		stackblock() + startloc));
+	argbackq = saveargbackq;
 	expdest = dest;
 	INTON;
 }

Modified: head/bin/sh/tests/expansion/Makefile
==============================================================================
--- head/bin/sh/tests/expansion/Makefile	Sat Mar  4 22:38:10 2017	(r314685)
+++ head/bin/sh/tests/expansion/Makefile	Sat Mar  4 22:58:34 2017	(r314686)
@@ -42,6 +42,8 @@ ${PACKAGE}FILES+=	cmdsubst17.0
 ${PACKAGE}FILES+=	cmdsubst18.0
 ${PACKAGE}FILES+=	cmdsubst19.0
 ${PACKAGE}FILES+=	cmdsubst20.0
+${PACKAGE}FILES+=	cmdsubst21.0
+${PACKAGE}FILES+=	cmdsubst22.0
 ${PACKAGE}FILES+=	export1.0
 ${PACKAGE}FILES+=	export2.0
 ${PACKAGE}FILES+=	export3.0

Added: head/bin/sh/tests/expansion/cmdsubst21.0
==============================================================================
--- /dev/null	00:00:00 1970	(empty, because file is newly added)
+++ head/bin/sh/tests/expansion/cmdsubst21.0	Sat Mar  4 22:58:34 2017	(r314686)
@@ -0,0 +1,6 @@
+# $FreeBSD$
+
+set -T
+trapped=''
+trap "trapped=x$trapped" TERM
+[ "x$($SH -c "kill $$")y" = xy ] && [ "$trapped" = x ]

Added: head/bin/sh/tests/expansion/cmdsubst22.0
==============================================================================
--- /dev/null	00:00:00 1970	(empty, because file is newly added)
+++ head/bin/sh/tests/expansion/cmdsubst22.0	Sat Mar  4 22:58:34 2017	(r314686)
@@ -0,0 +1,6 @@
+# $FreeBSD$
+
+set -T
+trapped=''
+trap "trapped=x$trapped" TERM
+[ "x$(:; kill $$)y" = xy ] && [ "$trapped" = x ]