ksmbd: remove follow symlinks support

Use  LOOKUP_NO_SYMLINKS flags for default lookup to prohibit the middle of
symlink component lookup and remove follow symlinks parameter support.
We re-implement it as reparse point later.

Test result:
smbclient -Ulinkinjeon%1234 //172.30.1.42/share -c
"get hacked/passwd passwd"
NT_STATUS_OBJECT_NAME_NOT_FOUND opening remote file \hacked\passwd

Cc: Ralph Böhme <slow@samba.org>
Cc: Steve French <smfrench@gmail.com>
Acked-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/smb2pdu.c

@@ -2632,13 +2632,9 @@ int smb2_open(struct ksmbd_work *work)
 		goto err_out1;
 	}
 
-	if (req->CreateOptions & FILE_DELETE_ON_CLOSE_LE) {
-		/*
-		 * On delete request, instead of following up, need to
-		 * look the current entity
-		 */
-		rc = ksmbd_vfs_kern_path(name, 0, &path, 1);
-		if (!rc) {
+	rc = ksmbd_vfs_kern_path(name, LOOKUP_NO_SYMLINKS, &path, 1);
+	if (!rc) {
+		if (req->CreateOptions & FILE_DELETE_ON_CLOSE_LE) {
 			/*
 			 * If file exists with under flags, return access
 			 * denied error.
@@ -2657,25 +2653,10 @@ int smb2_open(struct ksmbd_work *work)
 				path_put(&path);
 				goto err_out;
 			}
-		}
-	} else {
-		if (test_share_config_flag(work->tcon->share_conf,
-					   KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS)) {
-			/*
-			 * Use LOOKUP_FOLLOW to follow the path of
-			 * symlink in path buildup
-			 */
-			rc = ksmbd_vfs_kern_path(name, LOOKUP_FOLLOW, &path, 1);
-			if (rc) { /* Case for broken link ?*/
-				rc = ksmbd_vfs_kern_path(name, 0, &path, 1);
-			}
-		} else {
-			rc = ksmbd_vfs_kern_path(name, 0, &path, 1);
-			if (!rc && d_is_symlink(path.dentry)) {
-				rc = -EACCES;
-				path_put(&path);
-				goto err_out;
-			}
+		} else if (d_is_symlink(path.dentry)) {
+			rc = -EACCES;
+			path_put(&path);
+			goto err_out;
 		}
 	}
 
@@ -4751,12 +4732,8 @@ static int smb2_get_info_filesystem(struct ksmbd_work *work,
 	struct path path;
 	int rc = 0, len;
 	int fs_infoclass_size = 0;
-	int lookup_flags = 0;
-
-	if (test_share_config_flag(share, KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
-		lookup_flags = LOOKUP_FOLLOW;
 
-	rc = ksmbd_vfs_kern_path(share->path, lookup_flags, &path, 0);
+	rc = ksmbd_vfs_kern_path(share->path, LOOKUP_NO_SYMLINKS, &path, 0);
 	if (rc) {
 		pr_err("cannot create vfs path\n");
 		return -EIO;
@@ -5333,7 +5310,7 @@ static int smb2_rename(struct ksmbd_work *work,
 	}
 
 	ksmbd_debug(SMB, "new name %s\n", new_name);
-	rc = ksmbd_vfs_kern_path(new_name, 0, &path, 1);
+	rc = ksmbd_vfs_kern_path(new_name, LOOKUP_NO_SYMLINKS, &path, 1);
 	if (rc)
 		file_present = false;
 	else
@@ -5407,7 +5384,7 @@ static int smb2_create_link(struct ksmbd_work *work,
 	}
 
 	ksmbd_debug(SMB, "target name is %s\n", target_name);
-	rc = ksmbd_vfs_kern_path(link_name, 0, &path, 0);
+	rc = ksmbd_vfs_kern_path(link_name, LOOKUP_NO_SYMLINKS, &path, 0);
 	if (rc)
 		file_present = false;
 	else

fs/ksmbd/vfs.c

@@ -166,7 +166,7 @@ int ksmbd_vfs_create(struct ksmbd_work *work, const char *name, umode_t mode)
 	struct dentry *dentry;
 	int err;
 
-	dentry = kern_path_create(AT_FDCWD, name, &path, 0);
+	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_NO_SYMLINKS);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		if (err != -ENOENT)
@@ -203,7 +203,8 @@ int ksmbd_vfs_mkdir(struct ksmbd_work *work, const char *name, umode_t mode)
 	struct dentry *dentry;
 	int err;
 
-	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
+	dentry = kern_path_create(AT_FDCWD, name, &path,
+				  LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		if (err != -EEXIST)
@@ -588,16 +589,11 @@ int ksmbd_vfs_remove_file(struct ksmbd_work *work, char *name)
 	struct path path;
 	struct dentry *parent;
 	int err;
-	int flags = 0;
 
 	if (ksmbd_override_fsids(work))
 		return -ENOMEM;
 
-	if (test_share_config_flag(work->tcon->share_conf,
-				   KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
-		flags = LOOKUP_FOLLOW;
-
-	err = kern_path(name, flags, &path);
+	err = kern_path(name, LOOKUP_NO_SYMLINKS, &path);
 	if (err) {
 		ksmbd_debug(VFS, "can't get %s, err %d\n", name, err);
 		ksmbd_revert_fsids(work);
@@ -652,16 +648,11 @@ int ksmbd_vfs_link(struct ksmbd_work *work, const char *oldname,
 	struct path oldpath, newpath;
 	struct dentry *dentry;
 	int err;
-	int flags = 0;
 
 	if (ksmbd_override_fsids(work))
 		return -ENOMEM;
 
-	if (test_share_config_flag(work->tcon->share_conf,
-				   KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
-		flags = LOOKUP_FOLLOW;
-
-	err = kern_path(oldname, flags, &oldpath);
+	err = kern_path(oldname, LOOKUP_NO_SYMLINKS, &oldpath);
 	if (err) {
 		pr_err("cannot get linux path for %s, err = %d\n",
 		       oldname, err);
@@ -669,7 +660,7 @@ int ksmbd_vfs_link(struct ksmbd_work *work, const char *oldname,
 	}
 
 	dentry = kern_path_create(AT_FDCWD, newname, &newpath,
-				  flags | LOOKUP_REVAL);
+				  LOOKUP_NO_SYMLINKS | LOOKUP_REVAL);
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		pr_err("path create err for %s, err %d\n", newname, err);
@@ -788,7 +779,6 @@ int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
 	struct dentry *src_dent, *trap_dent, *src_child;
 	char *dst_name;
 	int err;
-	int flags;
 
 	dst_name = extract_last_component(newname);
 	if (!dst_name)
@@ -797,12 +787,8 @@ int ksmbd_vfs_fp_rename(struct ksmbd_work *work, struct ksmbd_file *fp,
 	src_dent_parent = dget_parent(fp->filp->f_path.dentry);
 	src_dent = fp->filp->f_path.dentry;
 
-	flags = LOOKUP_DIRECTORY;
-	if (test_share_config_flag(work->tcon->share_conf,
-				   KSMBD_SHARE_FLAG_FOLLOW_SYMLINKS))
-		flags |= LOOKUP_FOLLOW;
-
-	err = kern_path(newname, flags, &dst_path);
+	err = kern_path(newname, LOOKUP_NO_SYMLINKS | LOOKUP_DIRECTORY,
+			&dst_path);
 	if (err) {
 		ksmbd_debug(VFS, "Cannot get path for %s [%d]\n", newname, err);
 		goto out;
@@ -861,7 +847,7 @@ int ksmbd_vfs_truncate(struct ksmbd_work *work, const char *name,
 	int err = 0;
 
 	if (name) {
-		err = kern_path(name, 0, &path);
+		err = kern_path(name, LOOKUP_NO_SYMLINKS, &path);
 		if (err) {
 			pr_err("cannot get linux path for %s, err %d\n",
 			       name, err);