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

2 files changed, 5 insertions, 5 deletions

diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index ca3578993..e96a1d752 100644
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -723,15 +723,15 @@ lowbit64(uint64_t i)
 	return (__builtin_ffsll(i));
 }
 
-char *random_path = "/dev/random";
-char *urandom_path = "/dev/urandom";
+const char *random_path = "/dev/random";
+const char *urandom_path = "/dev/urandom";
 static int random_fd = -1, urandom_fd = -1;
 
 void
 random_init(void)
 {
-	VERIFY((random_fd = open(random_path, O_RDONLY)) != -1);
-	VERIFY((urandom_fd = open(urandom_path, O_RDONLY)) != -1);
+	VERIFY((random_fd = open(random_path, O_RDONLY | O_CLOEXEC)) != -1);
+	VERIFY((urandom_fd = open(urandom_path, O_RDONLY | O_CLOEXEC)) != -1);
 }
 
 void
diff --git a/lib/libzpool/util.c b/lib/libzpool/util.c
index 2da2375a1..20cabe7c2 100644
--- a/lib/libzpool/util.c
+++ b/lib/libzpool/util.c
@@ -259,7 +259,7 @@ pool_active(void *unused, const char *name, uint64_t guid,
 	 * Use ZFS_IOC_POOL_SYNC to confirm if a pool is active
 	 */
 
-	fd = open(ZFS_DEV, O_RDWR);
+	fd = open(ZFS_DEV, O_RDWR | O_CLOEXEC);
 	if (fd < 0)
 		return (-1);