UBUNTU: Ubuntu-4.13.0-45.50

[mirror_ubuntu-artful-kernel.git] / fs / super.c

diff --git a/fs/super.c b/fs/super.c
index 6bc3352adcf39fc5ed6cad77b5df5c9d7db3f9cc..4d486caa29a8e562223b173b807cab28cf8a04b6 100644 (file)
--- a/fs/super.c
+++ b/fs/super.c
@@ -1078,6 +1078,23 @@ 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
@@ -1087,7 +1104,7 @@ 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);
@@ -1099,7 +1116,7 @@ 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;
                }
 
                /*
@@ -1130,6 +1147,12 @@ 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:
@@ -1146,6 +1169,11 @@ 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);
 }