ksmbd: remove setattr preparations in set_file_basic_info()

Permission checking and copying over ownership information is the task
of the underlying filesystem not ksmbd. The order is also wrong here.
This modifies the inode before notify_change(). If notify_change() fails
this will have changed ownership nonetheless. All of this is unnecessary
though since the underlying filesystem's ->setattr handler will do all
this (if required) by itself.

Cc: Steve French <stfrench@microsoft.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Hyunchul Lee <hyc.lee@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/smb2pdu.c

@@ -5440,7 +5440,7 @@ static int set_file_basic_info(struct ksmbd_file *fp, char *buf,
 {
 	struct smb2_file_all_info *file_info;
 	struct iattr attrs;
-	struct iattr temp_attrs;
+	struct timespec64 ctime;
 	struct file *filp;
 	struct inode *inode;
 	struct user_namespace *user_ns;
@@ -5464,11 +5464,11 @@ static int set_file_basic_info(struct ksmbd_file *fp, char *buf,
 	}
 
 	if (file_info->ChangeTime) {
-		temp_attrs.ia_ctime = ksmbd_NTtimeToUnix(file_info->ChangeTime);
-		attrs.ia_ctime = temp_attrs.ia_ctime;
+		attrs.ia_ctime = ksmbd_NTtimeToUnix(file_info->ChangeTime);
+		ctime = attrs.ia_ctime;
 		attrs.ia_valid |= ATTR_CTIME;
 	} else {
-		temp_attrs.ia_ctime = inode->i_ctime;
+		ctime = inode->i_ctime;
 	}
 
 	if (file_info->LastWriteTime) {
@@ -5507,28 +5507,19 @@ static int set_file_basic_info(struct ksmbd_file *fp, char *buf,
 		rc = 0;
 	}
 
-	/*
-	 * HACK : set ctime here to avoid ctime changed
-	 * when file_info->ChangeTime is zero.
-	 */
-	attrs.ia_ctime = temp_attrs.ia_ctime;
-	attrs.ia_valid |= ATTR_CTIME;
-
 	if (attrs.ia_valid) {
 		struct dentry *dentry = filp->f_path.dentry;
 		struct inode *inode = d_inode(dentry);
 
 		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 			return -EACCES;
 
-		rc = setattr_prepare(user_ns, dentry, &attrs);
-		if (rc)
-			return -EINVAL;
-
 		inode_lock(inode);
-		setattr_copy(user_ns, inode, &attrs);
-		attrs.ia_valid &= ~ATTR_CTIME;
 		rc = notify_change(user_ns, dentry, &attrs, NULL);
+		if (!rc) {
+			inode->i_ctime = ctime;
+			mark_inode_dirty(inode);
+		}
 		inode_unlock(inode);
 	}
 	return rc;