ksmbd: validate share name from share config response

Share config response may contain the share name without casefolding as
it is known to the user space daemon. When it is present, casefold and
compare it to the share name the share config request was made with. If
they differ, we have a share config which is incompatible with the way
share config caching is done. This is the case when CONFIG_UNICODE is
not set, the share name contains non-ASCII characters, and those non-
ASCII characters do not match those in the share name known to user
space. In other words, when CONFIG_UNICODE is not set, UTF-8 share
names now work but are only case-insensitive in the ASCII range.
Signed-off-by: Atte Heikkilä <atteh.mailbox@gmail.com>
Acked-by: Tom Talpey <tom@talpey.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/ksmbd_netlink.h

@@ -163,7 +163,8 @@ struct ksmbd_share_config_response {
 	__u16	force_directory_mode;
 	__u16	force_uid;
 	__u16	force_gid;
-	__u32	reserved[128];		/* Reserved room */
+	__s8	share_name[KSMBD_REQ_MAX_SHARE_NAME];
+	__u32	reserved[112];		/* Reserved room */
 	__u32	veto_list_sz;
 	__s8	____payload[];
 };

fs/ksmbd/mgmt/share_config.c

@@ -16,6 +16,7 @@
 #include "user_config.h"
 #include "user_session.h"
 #include "../transport_ipc.h"
+#include "../misc.h"
 
 #define SHARE_HASH_BITS		3
 static DEFINE_HASHTABLE(shares_table, SHARE_HASH_BITS);
@@ -119,7 +120,8 @@ static int parse_veto_list(struct ksmbd_share_config *share,
 	return 0;
 }
 
-static struct ksmbd_share_config *share_config_request(const char *name)
+static struct ksmbd_share_config *share_config_request(struct unicode_map *um,
+						       const char *name)
 {
 	struct ksmbd_share_config_response *resp;
 	struct ksmbd_share_config *share = NULL;
@@ -133,6 +135,19 @@ static struct ksmbd_share_config *share_config_request(const char *name)
 	if (resp->flags == KSMBD_SHARE_FLAG_INVALID)
 		goto out;
 
+	if (*resp->share_name) {
+		char *cf_resp_name;
+		bool equal;
+
+		cf_resp_name = ksmbd_casefold_sharename(um, resp->share_name);
+		if (IS_ERR(cf_resp_name))
+			goto out;
+		equal = !strcmp(cf_resp_name, name);
+		kfree(cf_resp_name);
+		if (!equal)
+			goto out;
+	}
+
 	share = kzalloc(sizeof(struct ksmbd_share_config), GFP_KERNEL);
 	if (!share)
 		goto out;
@@ -190,7 +205,8 @@ static struct ksmbd_share_config *share_config_request(const char *name)
 	return share;
 }
 
-struct ksmbd_share_config *ksmbd_share_config_get(const char *name)
+struct ksmbd_share_config *ksmbd_share_config_get(struct unicode_map *um,
+						  const char *name)
 {
 	struct ksmbd_share_config *share;
 
@@ -202,7 +218,7 @@ struct ksmbd_share_config *ksmbd_share_config_get(const char *name)
 
 	if (share)
 		return share;
-	return share_config_request(name);
+	return share_config_request(um, name);
 }
 
 bool ksmbd_share_veto_filename(struct ksmbd_share_config *share,

fs/ksmbd/mgmt/share_config.h

@@ -9,6 +9,7 @@
 #include <linux/workqueue.h>
 #include <linux/hashtable.h>
 #include <linux/path.h>
+#include <linux/unicode.h>
 
 struct ksmbd_share_config {
 	char			*name;
@@ -74,7 +75,8 @@ 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(const char *name);
+struct ksmbd_share_config *ksmbd_share_config_get(struct unicode_map *um,
+						  const char *name);
 bool ksmbd_share_veto_filename(struct ksmbd_share_config *share,
 			       const char *filename);
 #endif /* __SHARE_CONFIG_MANAGEMENT_H__ */

fs/ksmbd/mgmt/tree_connect.c

@@ -26,7 +26,7 @@ ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
 	struct sockaddr *peer_addr;
 	int ret;
 
-	sc = ksmbd_share_config_get(share_name);
+	sc = ksmbd_share_config_get(conn->um, share_name);
 	if (!sc)
 		return status;
 
@@ -61,7 +61,7 @@ ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
 		struct ksmbd_share_config *new_sc;
 
 		ksmbd_share_config_del(sc);
-		new_sc = ksmbd_share_config_get(share_name);
+		new_sc = ksmbd_share_config_get(conn->um, share_name);
 		if (!new_sc) {
 			pr_err("Failed to update stale share config\n");
 			status.ret = -ESTALE;

fs/ksmbd/misc.c

@@ -227,7 +227,7 @@ void ksmbd_conv_path_to_windows(char *path)
 	strreplace(path, '/', '\\');
 }
 
-static char *casefold_sharename(struct unicode_map *um, const char *name)
+char *ksmbd_casefold_sharename(struct unicode_map *um, const char *name)
 {
 	char *cf_name;
 	int cf_len;
@@ -273,7 +273,7 @@ char *ksmbd_extract_sharename(struct unicode_map *um, const char *treename)
 		name = (pos + 1);
 
 	/* caller has to free the memory */
-	return casefold_sharename(um, name);
+	return ksmbd_casefold_sharename(um, name);
 }
 
 /**

fs/ksmbd/misc.h

@@ -20,6 +20,7 @@ int get_nlink(struct kstat *st);
 void ksmbd_conv_path_to_unix(char *path);
 void ksmbd_strip_last_slash(char *path);
 void ksmbd_conv_path_to_windows(char *path);
+char *ksmbd_casefold_sharename(struct unicode_map *um, const char *name);
 char *ksmbd_extract_sharename(struct unicode_map *um, const char *treename);
 char *convert_to_unix_name(struct ksmbd_share_config *share, const char *name);