ksmbd: override fsids for share path check

Sangsoo reported that a DAC denial error occurred when accessing
files through the ksmbd thread. This patch override fsids for share
path check.

Reported-by: Sangsoo Lee <constant.lee@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/mgmt/share_config.c

@@ -15,6 +15,7 @@
 #include "share_config.h"
 #include "user_config.h"
 #include "user_session.h"
+#include "../connection.h"
 #include "../transport_ipc.h"
 #include "../misc.h"
 
@@ -120,12 +121,13 @@ static int parse_veto_list(struct ksmbd_share_config *share,
 	return 0;
 }
 
-static struct ksmbd_share_config *share_config_request(struct unicode_map *um,
+static struct ksmbd_share_config *share_config_request(struct ksmbd_work *work,
 						       const char *name)
 {
 	struct ksmbd_share_config_response *resp;
 	struct ksmbd_share_config *share = NULL;
 	struct ksmbd_share_config *lookup;
+	struct unicode_map *um = work->conn->um;
 	int ret;
 
 	resp = ksmbd_ipc_share_config_request(name);
@@ -181,7 +183,14 @@ static struct ksmbd_share_config *share_config_request(struct unicode_map *um,
 				      KSMBD_SHARE_CONFIG_VETO_LIST(resp),
 				      resp->veto_list_sz);
 		if (!ret && share->path) {
+			if (__ksmbd_override_fsids(work, share)) {
+				kill_share(share);
+				share = NULL;
+				goto out;
+			}
+
 			ret = kern_path(share->path, 0, &share->vfs_path);
+			ksmbd_revert_fsids(work);
 			if (ret) {
 				ksmbd_debug(SMB, "failed to access '%s'\n",
 					    share->path);
@@ -214,7 +223,7 @@ static struct ksmbd_share_config *share_config_request(struct unicode_map *um,
 	return share;
 }
 
-struct ksmbd_share_config *ksmbd_share_config_get(struct unicode_map *um,
+struct ksmbd_share_config *ksmbd_share_config_get(struct ksmbd_work *work,
 						  const char *name)
 {
 	struct ksmbd_share_config *share;
@@ -227,7 +236,7 @@ struct ksmbd_share_config *ksmbd_share_config_get(struct unicode_map *um,
 
 	if (share)
 		return share;
-	return share_config_request(um, name);
+	return share_config_request(work, name);
 }
 
 bool ksmbd_share_veto_filename(struct ksmbd_share_config *share,

fs/smb/server/mgmt/share_config.h

@@ -11,6 +11,8 @@
 #include <linux/path.h>
 #include <linux/unicode.h>
 
+struct ksmbd_work;
+
 struct ksmbd_share_config {
 	char			*name;
 	char			*path;
@@ -68,7 +70,7 @@ 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(struct unicode_map *um,
+struct ksmbd_share_config *ksmbd_share_config_get(struct ksmbd_work *work,
 						  const char *name);
 bool ksmbd_share_veto_filename(struct ksmbd_share_config *share,
 			       const char *filename);

fs/smb/server/mgmt/tree_connect.c

@@ -16,17 +16,18 @@
 #include "user_session.h"
 
 struct ksmbd_tree_conn_status
-ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
-			const char *share_name)
+ksmbd_tree_conn_connect(struct ksmbd_work *work, const char *share_name)
 {
 	struct ksmbd_tree_conn_status status = {-ENOENT, NULL};
 	struct ksmbd_tree_connect_response *resp = NULL;
 	struct ksmbd_share_config *sc;
 	struct ksmbd_tree_connect *tree_conn = NULL;
 	struct sockaddr *peer_addr;
+	struct ksmbd_conn *conn = work->conn;
+	struct ksmbd_session *sess = work->sess;
 	int ret;
 
-	sc = ksmbd_share_config_get(conn->um, share_name);
+	sc = ksmbd_share_config_get(work, share_name);
 	if (!sc)
 		return status;
 
@@ -61,7 +62,7 @@ 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(conn->um, share_name);
+		new_sc = ksmbd_share_config_get(work, share_name);
 		if (!new_sc) {
 			pr_err("Failed to update stale share config\n");
 			status.ret = -ESTALE;

fs/smb/server/mgmt/tree_connect.h

@@ -13,6 +13,7 @@
 struct ksmbd_share_config;
 struct ksmbd_user;
 struct ksmbd_conn;
+struct ksmbd_work;
 
 enum {
 	TREE_NEW = 0,
@@ -50,8 +51,7 @@ static inline int test_tree_conn_flag(struct ksmbd_tree_connect *tree_conn,
 struct ksmbd_session;
 
 struct ksmbd_tree_conn_status
-ksmbd_tree_conn_connect(struct ksmbd_conn *conn, struct ksmbd_session *sess,
-			const char *share_name);
+ksmbd_tree_conn_connect(struct ksmbd_work *work, const char *share_name);
 void ksmbd_tree_connect_put(struct ksmbd_tree_connect *tcon);
 
 int ksmbd_tree_conn_disconnect(struct ksmbd_session *sess,

fs/smb/server/smb2pdu.c

@@ -1955,7 +1955,7 @@ int smb2_tree_connect(struct ksmbd_work *work)
 	ksmbd_debug(SMB, "tree connect request for tree %s treename %s\n",
 		    name, treename);
 
-	status = ksmbd_tree_conn_connect(conn, sess, name);
+	status = ksmbd_tree_conn_connect(work, name);
 	if (status.ret == KSMBD_TREE_CONN_STATUS_OK)
 		rsp->hdr.Id.SyncId.TreeId = cpu_to_le32(status.tree_conn->id);
 	else

fs/smb/server/smb_common.c

@@ -732,10 +732,10 @@ bool is_asterisk(char *p)
 	return p && p[0] == '*';
 }
 
-int ksmbd_override_fsids(struct ksmbd_work *work)
+int __ksmbd_override_fsids(struct ksmbd_work *work,
+		struct ksmbd_share_config *share)
 {
 	struct ksmbd_session *sess = work->sess;
-	struct ksmbd_share_config *share = work->tcon->share_conf;
 	struct cred *cred;
 	struct group_info *gi;
 	unsigned int uid;
@@ -775,6 +775,11 @@ int ksmbd_override_fsids(struct ksmbd_work *work)
 	return 0;
 }
 
+int ksmbd_override_fsids(struct ksmbd_work *work)
+{
+	return __ksmbd_override_fsids(work, work->tcon->share_conf);
+}
+
 void ksmbd_revert_fsids(struct ksmbd_work *work)
 {
 	const struct cred *cred;

fs/smb/server/smb_common.h

@@ -447,6 +447,8 @@ int ksmbd_extract_shortname(struct ksmbd_conn *conn,
 int ksmbd_smb_negotiate_common(struct ksmbd_work *work, unsigned int command);
 
 int ksmbd_smb_check_shared_mode(struct file *filp, struct ksmbd_file *curr_fp);
+int __ksmbd_override_fsids(struct ksmbd_work *work,
+			   struct ksmbd_share_config *share);
 int ksmbd_override_fsids(struct ksmbd_work *work);
 void ksmbd_revert_fsids(struct ksmbd_work *work);