[Precise,SRU] eCryptfs: Unlink lower inode when ecryptfs_create() fails

From: Tyler Hicks <tyhicks@canonical.com>

BugLink: http://bugs.launchpad.net/bugs/872905

ecryptfs_create() creates a lower inode, allocates an eCryptfs inode,
initializes the eCryptfs inode and cryptographic metadata attached to
the inode, and then writes the metadata to the header of the file.

If an error was to occur after the lower inode was created, an empty
lower file would be left in the lower filesystem. This is a problem
because ecryptfs_open() refuses to open any lower files which do not
have the appropriate metadata in the file header.

This patch properly unlinks the lower inode when an error occurs in the
later stages of ecryptfs_create(), reducing the chance that an empty
lower file will be left in the lower filesystem.

https://launchpad.net/bugs/872905

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Cc: John Johansen <john.johansen@canonical.com>
Cc: Colin Ian King <colin.king@canonical.com>
(cherry picked from commit 8bc2d3cf612994a960c2e8eaea37f6676f67082a)

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
 fs/ecryptfs/inode.c |   55 ++++++++++++++++++++++++++++++---------------------
 1 file changed, 32 insertions(+), 23 deletions(-)

On 07.08.2012 17:48, Tim Gardner wrote:
> From: Tyler Hicks <tyhicks@canonical.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/872905
> 
> ecryptfs_create() creates a lower inode, allocates an eCryptfs inode,
> initializes the eCryptfs inode and cryptographic metadata attached to
> the inode, and then writes the metadata to the header of the file.
> 
> If an error was to occur after the lower inode was created, an empty
> lower file would be left in the lower filesystem. This is a problem
> because ecryptfs_open() refuses to open any lower files which do not
> have the appropriate metadata in the file header.
> 
> This patch properly unlinks the lower inode when an error occurs in the
> later stages of ecryptfs_create(), reducing the chance that an empty
> lower file will be left in the lower filesystem.
> 
> https://launchpad.net/bugs/872905
> 
> Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
> Cc: John Johansen <john.johansen@canonical.com>
> Cc: Colin Ian King <colin.king@canonical.com>
> (cherry picked from commit 8bc2d3cf612994a960c2e8eaea37f6676f67082a)
> 
> Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
> ---
>  fs/ecryptfs/inode.c |   55 ++++++++++++++++++++++++++++++---------------------
>  1 file changed, 32 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
> index af11098..06f55bc 100644
> --- a/fs/ecryptfs/inode.c
> +++ b/fs/ecryptfs/inode.c
> @@ -143,6 +143,31 @@ static int ecryptfs_interpose(struct dentry *lower_dentry,
>  	return 0;
>  }
>  
> +static int ecryptfs_do_unlink(struct inode *dir, struct dentry *dentry,
> +			      struct inode *inode)
> +{
> +	struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
> +	struct inode *lower_dir_inode = ecryptfs_inode_to_lower(dir);
> +	struct dentry *lower_dir_dentry;
> +	int rc;
> +
> +	dget(lower_dentry);
> +	lower_dir_dentry = lock_parent(lower_dentry);
> +	rc = vfs_unlink(lower_dir_inode, lower_dentry);
> +	if (rc) {
> +		printk(KERN_ERR "Error in vfs_unlink; rc = [%d]\n", rc);
> +		goto out_unlock;
> +	}
> +	fsstack_copy_attr_times(dir, lower_dir_inode);
> +	set_nlink(inode, ecryptfs_inode_to_lower(inode)->i_nlink);
> +	inode->i_ctime = dir->i_ctime;
> +	d_drop(dentry);
> +out_unlock:
> +	unlock_dir(lower_dir_dentry);
> +	dput(lower_dentry);
> +	return rc;
> +}
> +
>  /**
>   * ecryptfs_create_underlying_file
>   * @lower_dir_inode: inode of the parent in the lower fs of the new file
> @@ -201,8 +226,10 @@ ecryptfs_do_create(struct inode *directory_inode,
>  	}
>  	inode = __ecryptfs_get_inode(lower_dentry->d_inode,
>  				     directory_inode->i_sb);
> -	if (IS_ERR(inode))
> +	if (IS_ERR(inode)) {
> +		vfs_unlink(lower_dir_dentry->d_inode, lower_dentry);
>  		goto out_lock;
> +	}
>  	fsstack_copy_attr_times(directory_inode, lower_dir_dentry->d_inode);
>  	fsstack_copy_inode_size(directory_inode, lower_dir_dentry->d_inode);
>  out_lock:
> @@ -284,7 +311,9 @@ ecryptfs_create(struct inode *directory_inode, struct dentry *ecryptfs_dentry,
>  	 * that this on disk file is prepared to be an ecryptfs file */
>  	rc = ecryptfs_initialize_file(ecryptfs_dentry, ecryptfs_inode);
>  	if (rc) {
> -		drop_nlink(ecryptfs_inode);
> +		ecryptfs_do_unlink(directory_inode, ecryptfs_dentry,
> +				   ecryptfs_inode);
> +		make_bad_inode(ecryptfs_inode);
>  		unlock_new_inode(ecryptfs_inode);
>  		iput(ecryptfs_inode);
>  		goto out;
> @@ -496,27 +525,7 @@ out_lock:
>  
>  static int ecryptfs_unlink(struct inode *dir, struct dentry *dentry)
>  {
> -	int rc = 0;
> -	struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
> -	struct inode *lower_dir_inode = ecryptfs_inode_to_lower(dir);
> -	struct dentry *lower_dir_dentry;
> -
> -	dget(lower_dentry);
> -	lower_dir_dentry = lock_parent(lower_dentry);
> -	rc = vfs_unlink(lower_dir_inode, lower_dentry);
> -	if (rc) {
> -		printk(KERN_ERR "Error in vfs_unlink; rc = [%d]\n", rc);
> -		goto out_unlock;
> -	}
> -	fsstack_copy_attr_times(dir, lower_dir_inode);
> -	set_nlink(dentry->d_inode,
> -		  ecryptfs_inode_to_lower(dentry->d_inode)->i_nlink);
> -	dentry->d_inode->i_ctime = dir->i_ctime;
> -	d_drop(dentry);
> -out_unlock:
> -	unlock_dir(lower_dir_dentry);
> -	dput(lower_dentry);
> -	return rc;
> +	return ecryptfs_do_unlink(dir, dentry, dentry->d_inode);
>  }
>  
>  static int ecryptfs_symlink(struct inode *dir, struct dentry *dentry,
>