ksmbd: casefold utf-8 share names and fix ascii lowercase conversion

strtolower() corrupts all UTF-8 share names that have a byte in the C0
(À ISO8859-1) to DE (Þ ISO8859-1) range, since the non-ASCII part of
ISO8859-1 is incompatible with UTF-8. Prevent this by checking that a
byte is in the ASCII range with isascii(), before the conversion to
lowercase with tolower(). Properly handle case-insensitivity of UTF-8
share names by casefolding them, but fallback to ASCII lowercase
conversion on failure or if CONFIG_UNICODE is not set. Refactor to move
the share name casefolding immediately after the share name extraction.
Also, make the associated constness corrections.

Signed-off-by: Atte Heikkilä <atteh.mailbox@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

4 files changed, 7 insertions, 17 deletions

diff --git a/fs/ksmbd/mgmt/share_config.c b/fs/ksmbd/mgmt/share_config.c
index c9bca1c2c834..5d039704c23c 100644
--- a/fs/ksmbd/mgmt/share_config.c
+++ b/fs/ksmbd/mgmt/share_config.c
@@ -26,7 +26,7 @@ struct ksmbd_veto_pattern {
 	struct list_head	list;
 };
 
-static unsigned int share_name_hash(char *name)
+static unsigned int share_name_hash(const char *name)
 {
 	return jhash(name, strlen(name), 0);
 }
@@ -72,7 +72,7 @@ __get_share_config(struct ksmbd_share_config *share)
 	return share;
 }
 
-static struct ksmbd_share_config *__share_lookup(char *name)
+static struct ksmbd_share_config *__share_lookup(const char *name)
 {
 	struct ksmbd_share_config *share;
 	unsigned int key = share_name_hash(name);
@@ -119,7 +119,7 @@ static int parse_veto_list(struct ksmbd_share_config *share,
 	return 0;
 }
 
-static struct ksmbd_share_config *share_config_request(char *name)
+static struct ksmbd_share_config *share_config_request(const char *name)
 {
 	struct ksmbd_share_config_response *resp;
 	struct ksmbd_share_config *share = NULL;
@@ -190,20 +190,10 @@ out:
 	return share;
 }
 
-static void strtolower(char *share_name)
-{
-	while (*share_name) {
-		*share_name = tolower(*share_name);
-		share_name++;
-	}
-}
-
-struct ksmbd_share_config *ksmbd_share_config_get(char *name)
+struct ksmbd_share_config *ksmbd_share_config_get(const char *name)
 {
 	struct ksmbd_share_config *share;
 
-	strtolower(name);
-
 	down_read(&shares_table_lock);
 	share = __share_lookup(name);
 	if (share)
diff --git a/fs/ksmbd/mgmt/share_config.h b/fs/ksmbd/mgmt/share_config.h
index 902f2cb1963a..7f7e89ecfe61 100644
--- a/fs/ksmbd/mgmt/share_config.h
+++ b/fs/ksmbd/mgmt/share_config.h
@@ -74,7 +74,7 @@ static inline void ksmbd_share_config_put(struct ksmbd_share_config *share)
 	__ksmbd_share_config_put(share);
 }
 
-struct ksmbd_share_config *ksmbd_share_config_get(char *name);
+struct ksmbd_share_config *ksmbd_share_config_get(const char *name);
 bool ksmbd_share_veto_filename(struct ksmbd_share_config *share,
 			       const char *filename);
 #endif /* __SHARE_CONFIG_MANAGEMENT_H__ */
diff --git a/fs/ksmbd/mgmt/tree_connect.c b/fs/ksmbd/mgmt/tree_connect.c
index 97ab7987df6e..867c0286b901 100644
--- a/fs/ksmbd/mgmt/tree_connect.c
+++ b/fs/ksmbd/mgmt/tree_connect.c
@@ -17,7 +17,7 @@
 
 struct ksmbd_tree_conn_status
 ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
-			char *share_name)
+			const char *share_name)
 {
 	struct ksmbd_tree_conn_status status = {-ENOENT, NULL};
 	struct ksmbd_tree_connect_response *resp = NULL;
diff --git a/fs/ksmbd/mgmt/tree_connect.h b/fs/ksmbd/mgmt/tree_connect.h
index 71e50271dccf..0f97ddc1e39c 100644
--- a/fs/ksmbd/mgmt/tree_connect.h
+++ b/fs/ksmbd/mgmt/tree_connect.h
@@ -42,7 +42,7 @@ struct ksmbd_session;
 
 struct ksmbd_tree_conn_status
 ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
-			char *share_name);
+			const char *share_name);
 
 int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,
 			       struct ksmbd_tree_connect *tree_conn);