Restrict filesystem creation if name referred either '.' or '..'

This change restricts filesystem creation if the given name
contains either '.' or '..'

Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Signed-off-by: TulsiJain <tulsi.jain@delphix.com>
Closes #8842
Closes #8564

include/zfs_namecheck.h

@@ -43,6 +43,8 @@ typedef enum {
 	NAME_ERR_RESERVED,		/* entire name is reserved */
 	NAME_ERR_DISKLIKE,		/* reserved disk name (c[0-9].*) */
 	NAME_ERR_TOOLONG,		/* name is too long */
+	NAME_ERR_SELF_REF,		/* reserved self path name ('.') */
+	NAME_ERR_PARENT_REF,		/* reserved parent path name ('..') */
 	NAME_ERR_NO_AT,			/* permission set is missing '@' */
 } namecheck_err_t;
 

lib/libzfs/libzfs_dataset.c

@@ -197,6 +197,16 @@ zfs_validate_name(libzfs_handle_t *hdl, const char *path, int type,
 				    "reserved disk name"));
 				break;
 
+			case NAME_ERR_SELF_REF:
+				zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+				    "self reference, '.' is found in name"));
+				break;
+
+			case NAME_ERR_PARENT_REF:
+				zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+				    "parent reference, '..' is found in name"));
+				break;
+
 			default:
 				zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
 				    "(%d) not defined"), why);

module/zcommon/zfs_namecheck.c

@@ -232,6 +232,27 @@ entity_namecheck(const char *path, namecheck_err_t *why, char *what)
 			}
 		}
 
+		if (*end == '\0' || *end == '/') {
+			int component_length = end - start;
+			/* Validate the contents of this component is not '.' */
+			if (component_length == 1) {
+				if (start[0] == '.') {
+					if (why)
+						*why = NAME_ERR_SELF_REF;
+					return (-1);
+				}
+			}
+
+			/* Validate the content of this component is not '..' */
+			if (component_length == 2) {
+				if (start[0] == '.' && start[1] == '.') {
+					if (why)
+						*why = NAME_ERR_PARENT_REF;
+					return (-1);
+				}
+			}
+		}
+
 		/* Snapshot or bookmark delimiter found */
 		if (*end == '@' || *end == '#') {
 			/* Multiple delimiters are not allowed */

tests/zfs-tests/tests/functional/cli_root/zfs_create/zfs_create_009_neg.ksh

@@ -90,7 +90,9 @@ set -A args  "$TESTPOOL/" "$TESTPOOL//blah" "$TESTPOOL/@blah" \
 	"$TESTPOOL/blah*blah" "$TESTPOOL/blah blah" \
 	"-s $TESTPOOL/$TESTFS1" "-b 1092 $TESTPOOL/$TESTFS1" \
 	"-b 64k $TESTPOOL/$TESTFS1" "-s -b 32k $TESTPOOL/$TESTFS1" \
-	"$TESTPOOL/$BYND_MAX_NAME" "$TESTPOOL/$BYND_NEST_LIMIT"
+	"$TESTPOOL/$BYND_MAX_NAME" "$TESTPOOL/$BYND_NEST_LIMIT" \
+	"$TESTPOOL/." "$TESTPOOL/.." "$TESTPOOL/../blah" "$TESTPOOL/./blah" \
+	"$TESTPOOL/blah/./blah" "$TESTPOOL/blah/../blah"
 
 log_assert "Verify 'zfs create <filesystem>' fails with bad <filesystem> argument."