lib/: set O_CLOEXEC on all fds

As found by
  git grep -E '(open|setmntent|pipe2?)\(' |
    grep -vE '((zfs|zpool)_|fd|dl|lzc_re|pidfile_|g_)open\('

FreeBSD's pidfile_open() says nothing about the flags of the files it
opens, but we can't do anything about it anyway; the implementation does
open all files with O_CLOEXEC

Consider this output with zpool.d/media appended with
"pid=$$; (ls -l /proc/$pid/fd > /dev/tty)":
  $ /sbin/zpool iostat -vc media
  lrwx------ 0 -> /dev/pts/0
  l-wx------ 1 -> 'pipe:[3278500]'
  l-wx------ 2 -> /dev/null
  lrwx------ 3 -> /dev/zfs
  lr-x------ 4 -> /proc/31895/mounts
  lrwx------ 5 -> /dev/zfs
  lr-x------ 10 -> /usr/lib/zfs-linux/zpool.d/media
vs
  $ ./zpool iostat -vc vendor,upath,iostat,media
  lrwx------ 0 -> /dev/pts/0
  l-wx------ 1 -> 'pipe:[3279887]'
  l-wx------ 2 -> /dev/null
  lr-x------ 10 -> /usr/lib/zfs-linux/zpool.d/media

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Ahelenia Ziemiańska <[email protected]>
Closes #11866

1 files changed, 3 insertions, 7 deletions

diff --git a/lib/libzfs/libzfs_util.c b/lib/libzfs/libzfs_util.c
index 7c2f84c7a..01537b535 100644
--- a/lib/libzfs/libzfs_util.c
+++ b/lib/libzfs/libzfs_util.c
@@ -884,13 +884,13 @@ libzfs_run_process_impl(const char *path, char *argv[], char *env[], int flags,
 	 * Setup a pipe between our child and parent process if we're
 	 * reading stdout.
 	 */
-	if ((lines != NULL) && pipe(link) == -1)
+	if ((lines != NULL) && pipe2(link, O_CLOEXEC) == -1)
 		return (-EPIPE);
 
 	pid = vfork();
 	if (pid == 0) {
 		/* Child process */
-		devnull_fd = open("/dev/null", O_WRONLY);
+		devnull_fd = open("/dev/null", O_WRONLY | O_CLOEXEC);
 
 		if (devnull_fd < 0)
 			_exit(-1);
@@ -900,15 +900,11 @@ libzfs_run_process_impl(const char *path, char *argv[], char *env[], int flags,
 		else if (lines != NULL) {
 			/* Save the output to lines[] */
 			dup2(link[1], STDOUT_FILENO);
-			close(link[0]);
-			close(link[1]);
 		}
 
 		if (!(flags & STDERR_VERBOSE))
 			(void) dup2(devnull_fd, STDERR_FILENO);
 
-		close(devnull_fd);
-
 		if (flags & NO_DEFAULT_PATH) {
 			if (env == NULL)
 				execv(path, argv);
@@ -1144,7 +1140,7 @@ zfs_path_to_zhandle(libzfs_handle_t *hdl, const char *path, zfs_type_t argtype)
 	}
 
 	/* Reopen MNTTAB to prevent reading stale data from open file */
-	if (freopen(MNTTAB, "r", hdl->libzfs_mnttab) == NULL)
+	if (freopen(MNTTAB, "re", hdl->libzfs_mnttab) == NULL)
 		return (NULL);
 
 	if (getextmntent(path, &entry, &statbuf) != 0)