Re: [PATCH] ecryptfs lower file handling code issues

[Dmitriy Monakhov <dmonakhov@sw.ru>]

Dmitriy Monakhov <dmonakhov@openvz.org> writes:

> eCryptfs lower file handling code has several issues:
>   - Retval from prepare_write()/commit_writ() was't checked to equality 
>     to AOP_TRUNCATED_PAGE.
>   - In some places page was't unmapped and unlocked after error.
it is easy to retproduce:
##Prepare FS
dd if=/dev/zero of=FS.img bs=1M count=64
mkfs.ext3 -F FS.img 
mkdir crypt_root
mkdir crypt_private
mount FS.img crypt_private/ -oloop
mount -t ecryptfs crypt_private/ crypt_root/ -ocipher=aes
## exhaust all available space, and provoke ENOSPC condition.
for ((i=0;i<100;i++));do dd if=/dev/zero of=crypt_root/file$i bs=1M count=1;done
###### after  this we got folowing errors on console:
#process_new_file: Error preparing to write header page out; rc = [-28]
#ecryptfs_commit_write: Error processing new file; rc = [-28]
#write_zeros: Error attempting to write zero's to remainder of page at index [0x0000000000000000]
#ecryptfs_fill_zeros: write_zeros(file=[f561bde0], index=[0x0000000000000000], old_end_pos_in_page=[d], (PAGE_CACHE_SIZE - new_end_pos_in_page=[-1])=[d]) returned [0]
#grow_file: Error attempting to fill zeros in file; rc = [-28]

# After prepare_write() failed in process_new_file() page was't unlocked,
# so leter umount will stuck forever in D state. 
umount crypt_root/
umount crypt_private/ ## stuck forever here.
>
> Signed-off-by: Dmitriy Monakhov <dmonakhov@openvz.org>
> --------------   
> diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
> index 06843d2..27ac9ef 100644
> --- a/fs/ecryptfs/mmap.c
> +++ b/fs/ecryptfs/mmap.c
> @@ -391,12 +391,14 @@ out:
>  	return rc;
>  }
>  
> -static void ecryptfs_unmap_and_release_lower_page(struct page *lower_page)
> +static void ecryptfs_unmap_and_release_lower_page(struct page *lower_page,
> +		int page_locked)
>  {
>  	kunmap(lower_page);
>  	ecryptfs_printk(KERN_DEBUG, "Unlocking lower page with index = "
>  			"[0x%.16x]\n", lower_page->index);
> -	unlock_page(lower_page);
> +	if (page_locked)
> +		unlock_page(lower_page);
>  	page_cache_release(lower_page);
>  }
>  
> @@ -417,6 +419,7 @@ ecryptfs_write_inode_size_to_header(struct file *lower_file,
>  	char *header_virt;
>  	const struct address_space_operations *lower_a_ops;
>  	u64 file_size;
> +	int pg_locked = 1;
>  
>  	rc = ecryptfs_grab_and_map_lower_page(&header_page, &header_virt,
>  					      lower_inode, 0);
> @@ -427,6 +430,12 @@ ecryptfs_write_inode_size_to_header(struct file *lower_file,
>  	}
>  	lower_a_ops = lower_inode->i_mapping->a_ops;
>  	rc = lower_a_ops->prepare_write(lower_file, header_page, 0, 8);
> +	if (rc) {
> +		if (rc == AOP_TRUNCATED_PAGE)
> +			pg_locked = 0;
> +		ecryptfs_unmap_and_release_lower_page(header_page, pg_locked);
> +		goto out;
> +	}
>  	file_size = (u64)i_size_read(inode);
>  	ecryptfs_printk(KERN_DEBUG, "Writing size: [0x%.16x]\n", file_size);
>  	file_size = cpu_to_be64(file_size);
> @@ -435,7 +444,9 @@ ecryptfs_write_inode_size_to_header(struct file *lower_file,
>  	if (rc < 0)
>  		ecryptfs_printk(KERN_ERR, "Error commiting header page "
>  				"write\n");
> -	ecryptfs_unmap_and_release_lower_page(header_page);
> +	if (rc == AOP_TRUNCATED_PAGE)
> +		pg_locked = 0;
> +	ecryptfs_unmap_and_release_lower_page(header_page, pg_locked);
>  	lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
>  	mark_inode_dirty_sync(inode);
>  out:
> @@ -468,7 +479,10 @@ int ecryptfs_get_lower_page(struct page **lower_page, struct inode *lower_inode,
>  	}
>  out:
>  	if (rc && (*lower_page)) {
> -		ecryptfs_unmap_and_release_lower_page(*lower_page);
> +		int pg_locked = 1;
> +		if (rc == AOP_TRUNCATED_PAGE)
> +			pg_locked = 0;
> +		ecryptfs_unmap_and_release_lower_page(*lower_page, pg_locked);
>  		(*lower_page) = NULL;
>  	}
>  	return rc;
> @@ -484,16 +498,19 @@ ecryptfs_commit_lower_page(struct page *lower_page, struct inode *lower_inode,
>  			   struct file *lower_file, int byte_offset,
>  			   int region_size)
>  {
> +	int pg_locked = 1;
>  	int rc = 0;
>  
>  	rc = lower_inode->i_mapping->a_ops->commit_write(
>  		lower_file, lower_page, byte_offset, region_size);
> +	if (rc == AOP_TRUNCATED_PAGE)
> +		pg_locked = 0;
>  	if (rc < 0) {
>  		ecryptfs_printk(KERN_ERR,
>  				"Error committing write; rc = [%d]\n", rc);
>  	} else
>  		rc = 0;
> -	ecryptfs_unmap_and_release_lower_page(lower_page);
> +	ecryptfs_unmap_and_release_lower_page(lower_page, pg_locked);
>  	return rc;
>  }
>  
> @@ -541,6 +558,7 @@ process_new_file(struct ecryptfs_crypt_stat *crypt_stat,
>  	int current_header_page = 0;
>  	int header_pages;
>  	int more_header_data_to_be_written = 1;
> +	int pg_locked = 1;
>  
>  	lower_inode = ecryptfs_inode_to_lower(inode);
>  	lower_file = ecryptfs_file_to_lower(file);
> @@ -563,6 +581,10 @@ process_new_file(struct ecryptfs_crypt_stat *crypt_stat,
>  		rc = lower_a_ops->prepare_write(lower_file, header_page, 0,
>  						PAGE_CACHE_SIZE);
>  		if (rc) {
> +			if (rc == AOP_TRUNCATED_PAGE)
> +				pg_locked = 0;
> +			ecryptfs_unmap_and_release_lower_page(header_page,
> +				pg_locked);
>  			ecryptfs_printk(KERN_ERR, "Error preparing to write "
>  					"header page out; rc = [%d]\n", rc);
>  			goto out;
> @@ -579,7 +601,7 @@ process_new_file(struct ecryptfs_crypt_stat *crypt_stat,
>  				rc = -EIO;
>  				memset(header_virt, 0, PAGE_CACHE_SIZE);
>  				ecryptfs_unmap_and_release_lower_page(
> -					header_page);
> +					header_page, pg_locked);
>  				goto out;
>  			}
>  			if (current_header_page == 0)
> @@ -588,7 +610,9 @@ process_new_file(struct ecryptfs_crypt_stat *crypt_stat,
>  		}
>  		rc = lower_a_ops->commit_write(lower_file, header_page, 0,
>  					       PAGE_CACHE_SIZE);
> -		ecryptfs_unmap_and_release_lower_page(header_page);
> +		if (rc == AOP_TRUNCATED_PAGE)
> +			pg_locked = 0;
> +		ecryptfs_unmap_and_release_lower_page(header_page, pg_locked);
>  		if (rc < 0) {
>  			ecryptfs_printk(KERN_ERR,
>  					"Error commiting header page write; "