svn commit: r250827 - in head: lib/libc/gen tools/regression/lib/libc/gen

[Jilles Tjoelker]

Author: jilles
Date: Mon May 20 17:31:18 2013
New Revision: 250827
URL: http://svnweb.freebsd.org/changeset/base/250827

Log:
  popen(): Add 'e' mode character to set close-on-exec on the new fd.
  
  If 'e' is used, the kernel must support the recently added pipe2() system
  call.
  
  The use of pipe2() with O_CLOEXEC also fixes race conditions between
  concurrent popen() calls from different threads, even if the close-on-exec
  flag on the fd of the returned FILE is later cleared (because popen() closes
  all file descriptors from earlier popen() calls in the child process).
  Therefore, this approach should be used in all cases when pipe2() can be
  assumed present.
  
  The old version of popen() rejects "re" and "we" but treats "r+e" like "r+".

Modified:
  head/lib/libc/gen/popen.3
  head/lib/libc/gen/popen.c
  head/tools/regression/lib/libc/gen/test-popen.c

Modified: head/lib/libc/gen/popen.3
==============================================================================
--- head/lib/libc/gen/popen.3	Mon May 20 15:11:30 2013	(r250826)
+++ head/lib/libc/gen/popen.3	Mon May 20 17:31:18 2013	(r250827)
@@ -28,7 +28,7 @@
 .\"     @(#)popen.3	8.2 (Berkeley) 5/3/95
 .\" $FreeBSD$
 .\"
-.Dd May 3, 1995
+.Dd May 20, 2013
 .Dt POPEN 3
 .Os
 .Sh NAME
@@ -79,6 +79,11 @@ for writing, or
 .Ql r+
 for reading and writing.
 .Pp
+A letter
+.Ql e
+may be appended to that to request that the underlying file descriptor
+be set close-on-exec.
+.Pp
 The
 .Fa command
 argument is a pointer to a null-terminated string

Modified: head/lib/libc/gen/popen.c
==============================================================================
--- head/lib/libc/gen/popen.c	Mon May 20 15:11:30 2013	(r250826)
+++ head/lib/libc/gen/popen.c	Mon May 20 17:31:18 2013	(r250827)
@@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
 
 #include <signal.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -71,10 +72,11 @@ popen(command, type)
 {
 	struct pid *cur;
 	FILE *iop;
-	int pdes[2], pid, twoway;
+	int pdes[2], pid, twoway, cloexec;
 	char *argv[4];
 	struct pid *p;
 
+	cloexec = strchr(type, 'e') != NULL;
 	/*
 	 * Lite2 introduced two-way popen() pipes using _socketpair().
 	 * FreeBSD's pipe() is bidirectional, so we use that.
@@ -84,10 +86,11 @@ popen(command, type)
 		type = "r+";
 	} else  {
 		twoway = 0;
-		if ((*type != 'r' && *type != 'w') || type[1])
+		if ((*type != 'r' && *type != 'w') ||
+		    (type[1] && (type[1] != 'e' || type[2])))
 			return (NULL);
 	}
-	if (pipe(pdes) < 0)
+	if ((cloexec ? pipe2(pdes, O_CLOEXEC) : pipe(pdes)) < 0)
 		return (NULL);
 
 	if ((cur = malloc(sizeof(struct pid))) == NULL) {
@@ -120,20 +123,29 @@ popen(command, type)
 			 * the compiler is free to corrupt all the local
 			 * variables.
 			 */
-			(void)_close(pdes[0]);
+			if (!cloexec)
+				(void)_close(pdes[0]);
 			if (pdes[1] != STDOUT_FILENO) {
 				(void)_dup2(pdes[1], STDOUT_FILENO);
-				(void)_close(pdes[1]);
+				if (!cloexec)
+					(void)_close(pdes[1]);
 				if (twoway)
 					(void)_dup2(STDOUT_FILENO, STDIN_FILENO);
-			} else if (twoway && (pdes[1] != STDIN_FILENO))
+			} else if (twoway && (pdes[1] != STDIN_FILENO)) {
 				(void)_dup2(pdes[1], STDIN_FILENO);
+				if (cloexec)
+					(void)_fcntl(pdes[1], F_SETFD, 0);
+			} else if (cloexec)
+				(void)_fcntl(pdes[1], F_SETFD, 0);
 		} else {
 			if (pdes[0] != STDIN_FILENO) {
 				(void)_dup2(pdes[0], STDIN_FILENO);
-				(void)_close(pdes[0]);
-			}
-			(void)_close(pdes[1]);
+				if (!cloexec)
+					(void)_close(pdes[0]);
+			} else if (cloexec)
+				(void)_fcntl(pdes[0], F_SETFD, 0);
+			if (!cloexec)
+				(void)_close(pdes[1]);
 		}
 		SLIST_FOREACH(p, &pidlist, next)
 			(void)_close(fileno(p->fp));

Modified: head/tools/regression/lib/libc/gen/test-popen.c
==============================================================================
--- head/tools/regression/lib/libc/gen/test-popen.c	Mon May 20 15:11:30 2013	(r250826)
+++ head/tools/regression/lib/libc/gen/test-popen.c	Mon May 20 17:31:18 2013	(r250827)
@@ -70,10 +70,10 @@ main(int argc, char *argv[])
 	FILE *fp, *fp2;
 	int i, j, status;
 	const char *mode;
-	const char *allmodes[] = { "r", "w", "r+" };
-	const char *rmodes[] = { "r", "r+" };
-	const char *wmodes[] = { "w", "r+" };
-	const char *rwmodes[] = { "r+" };
+	const char *allmodes[] = { "r", "w", "r+", "re", "we", "r+e", "re+" };
+	const char *rmodes[] = { "r", "r+", "re", "r+e", "re+" };
+	const char *wmodes[] = { "w", "r+", "we", "r+e", "re+" };
+	const char *rwmodes[] = { "r+", "r+e", "re+" };
 	char buf[80];
 	struct sigaction act, oact;