3 files changed, 11 insertions, 1 deletions

diff --git a/sbin/mount/mntopts.h b/sbin/mount/mntopts.h
index 418bf8012232..924ead253890 100644
--- a/sbin/mount/mntopts.h
+++ b/sbin/mount/mntopts.h
@@ -58,6 +58,7 @@ struct mntopt {
 #define MOPT_ACLS		{ "acls",	0, MNT_ACLS, 0 }
 #define MOPT_NFS4ACLS		{ "nfsv4acls",	0, MNT_NFS4ACLS, 0 }
 #define MOPT_AUTOMOUNTED	{ "automounted",0, MNT_AUTOMOUNTED, 0 }
+#define MOPT_UNTRUSTED		{ "untrusted",  0, MNT_UNTRUSTED, 0 }
 
 /* Control flags. */
 #define MOPT_FORCE		{ "force",	0, MNT_FORCE, 0 }
@@ -93,7 +94,8 @@ struct mntopt {
 	MOPT_MULTILABEL,						\
 	MOPT_ACLS,							\
 	MOPT_NFS4ACLS,							\
-	MOPT_AUTOMOUNTED
+	MOPT_AUTOMOUNTED,						\
+	MOPT_UNTRUSTED
 
 void getmntopts(const char *, const struct mntopt *, int *, int *);
 void rmslashes(char *, char *);
diff --git a/sbin/mount/mount.8 b/sbin/mount/mount.8
index 27b5885240b6..7ff94fb7c165 100644
--- a/sbin/mount/mount.8
+++ b/sbin/mount/mount.8
@@ -355,6 +355,12 @@ Lookups will be done in the mounted file system first.
 If those operations fail due to a non-existent file the underlying
 directory is then accessed.
 All creates are done in the mounted file system.
+.It Cm untrusted
+The file system is untrusted and the kernel should use more
+extensive checks on the file-system's metadata before using it.
+This option is intended to be used when mounting file systems
+from untrusted media such as USB memory sticks or other
+externally-provided media.
 .El
 .Pp
 Any additional options specific to a file system type that is not
diff --git a/sbin/mount/mount.c b/sbin/mount/mount.c
index adab70d5eba5..3f35baccce22 100644
--- a/sbin/mount/mount.c
+++ b/sbin/mount/mount.c
@@ -118,6 +118,7 @@ static struct opt {
 	{ MNT_GJOURNAL,		"gjournal" },
 	{ MNT_AUTOMOUNTED,	"automounted" },
 	{ MNT_VERIFIED,		"verified" },
+	{ MNT_UNTRUSTED,	"untrusted" },
 	{ 0, NULL }
 };
 
@@ -972,6 +973,7 @@ flags2opts(int flags)
 	if (flags & MNT_MULTILABEL)	res = catopt(res, "multilabel");
 	if (flags & MNT_ACLS)		res = catopt(res, "acls");
 	if (flags & MNT_NFS4ACLS)	res = catopt(res, "nfsv4acls");
+	if (flags & MNT_UNTRUSTED)	res = catopt(res, "untrusted");
 
 	return (res);
 }