X-Git-Url: https://git.proxmox.com/?a=blobdiff_plain;f=fs%2Fsuper.c;h=36c4a3c73a0170c7a4fbd8e03bf64d59014c0272;hb=37c459e9dbc9b0809511d86f46b63b7c8994799d;hp=1709ed029a2cae70c3d4a6cccccca760a0ad003f;hpb=01e0d6037de687fd3bb8b45ab1376e8322c1fcc9;p=mirror_ubuntu-zesty-kernel.git

diff --git a/fs/super.c b/fs/super.c
index 1709ed029a2c..36c4a3c73a01 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -469,7 +469,7 @@ struct super_block *sget_userns(struct file_system_type *type,
 	struct super_block *old;
 	int err;
 
-	if (!(flags & MS_KERNMOUNT) &&
+	if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) &&
 	    !(type->fs_flags & FS_USERNS_MOUNT) &&
 	    !capable(CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
@@ -499,7 +499,7 @@ retry:
 	}
 	if (!s) {
 		spin_unlock(&sb_lock);
-		s = alloc_super(type, flags, user_ns);
+		s = alloc_super(type, (flags & ~MS_SUBMOUNT), user_ns);
 		if (!s)
 			return ERR_PTR(-ENOMEM);
 		goto retry;
@@ -540,8 +540,15 @@ struct super_block *sget(struct file_system_type *type,
 {
 	struct user_namespace *user_ns = current_user_ns();
 
+	/* We don't yet pass the user namespace of the parent
+	 * mount through to here so always use &init_user_ns
+	 * until that changes.
+	 */
+	if (flags & MS_SUBMOUNT)
+		user_ns = &init_user_ns;
+
 	/* Ensure the requestor has permissions over the target filesystem */
-	if (!(flags & MS_KERNMOUNT) && !ns_capable(user_ns, CAP_SYS_ADMIN))
+	if (!(flags & (MS_KERNMOUNT|MS_SUBMOUNT)) && !ns_capable(user_ns, CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
 
 	return sget_userns(type, test, set, flags, user_ns, data);
@@ -1072,6 +1079,23 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 	if (IS_ERR(bdev))
 		return ERR_CAST(bdev);
 
+	if (current_user_ns() != &init_user_ns) {
+		/*
+		 * For userns mounts, disallow mounting if bdev is open for
+		 * writing
+		 */
+		if (!atomic_dec_unless_positive(&bdev->bd_inode->i_writecount)) {
+			error = -EBUSY;
+			goto error_bdev;
+		}
+		if (bdev->bd_contains != bdev &&
+		    !atomic_dec_unless_positive(&bdev->bd_contains->bd_inode->i_writecount)) {
+			atomic_inc(&bdev->bd_inode->i_writecount);
+			error = -EBUSY;
+			goto error_bdev;
+		}
+	}
+
 	/*
 	 * once the super is inserted into the list by sget, s_umount
 	 * will protect the lockfs code from trying to start a snapshot
@@ -1081,7 +1105,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 	if (bdev->bd_fsfreeze_count > 0) {
 		mutex_unlock(&bdev->bd_fsfreeze_mutex);
 		error = -EBUSY;
-		goto error_bdev;
+		goto error_inc;
 	}
 	s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC,
 		 bdev);
@@ -1093,7 +1117,7 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 		if ((flags ^ s->s_flags) & MS_RDONLY) {
 			deactivate_locked_super(s);
 			error = -EBUSY;
-			goto error_bdev;
+			goto error_inc;
 		}
 
 		/*
@@ -1124,6 +1148,12 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
 
 error_s:
 	error = PTR_ERR(s);
+error_inc:
+	if (current_user_ns() != &init_user_ns) {
+		atomic_inc(&bdev->bd_inode->i_writecount);
+		if (bdev->bd_contains != bdev)
+			atomic_inc(&bdev->bd_contains->bd_inode->i_writecount);
+	}
 error_bdev:
 	blkdev_put(bdev, mode);
 error:
@@ -1140,6 +1170,11 @@ void kill_block_super(struct super_block *sb)
 	generic_shutdown_super(sb);
 	sync_blockdev(bdev);
 	WARN_ON_ONCE(!(mode & FMODE_EXCL));
+	if (sb->s_user_ns != &init_user_ns) {
+		atomic_inc(&bdev->bd_inode->i_writecount);
+		if (bdev->bd_contains != bdev)
+			atomic_inc(&bdev->bd_contains->bd_inode->i_writecount);
+	}
 	blkdev_put(bdev, mode | FMODE_EXCL);
 }