linux-ext4 - Re: [Ext4 Secure Delete 5/7v4] ext4: Secure Delete: Secure delete directory entry

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Date:	Fri, 07 Oct 2011 10:59:30 -0700
From:	Allison Henderson <achender@...ux.vnet.ibm.com>
To:	djwong@...ibm.com
CC:	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [Ext4 Secure Delete 5/7v4] ext4: Secure Delete: Secure delete
 directory entry

On 10/07/2011 10:22 AM, Darrick J. Wong wrote:
> On Fri, Oct 07, 2011 at 12:11:03AM -0700, Allison Henderson wrote:
>> This patch zeros or randomizes a files directory entry when a file
> <snip>
>> @@ -1669,7 +1672,38 @@ static int ext4_delete_entry(handle_t *handle,
>>   				de->inode = 0;
>>   			dir->i_version++;
>>   			BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
>> -			err = ext4_handle_dirty_metadata(handle, dir, bh);
>> +
>> +			/*
>> +			 * If the secure remove flag is on, zero
>> +			 * or randomize the entry and write it out
>> +			 * to the disk
>> +			 */
>> +			if (flags&  EXT4_DEL_ENTRY_ZERO) {
>> +				memset(de->name, 0x00, de->name_len);
>> +				de->file_type = 0;
>> +			} else if (flags&  EXT4_DEL_ENTRY_RAND) {
>> +				get_random_bytes(de->name, de->name_len);
>> +				get_random_bytes(&(de->file_type),
>> +					sizeof(de->file_type));
> 
> Seeing as name_len and file_type precede name, you could probably reduce this
> to one call that zaps all three.  Same for the zero-out case.
> 
> Also you might want to make both of these name-erasing calls zap the space
> between the end of the name and the end of the record, just in case there's old
> filename component still lurking in that space.  (Yes, paranoia...)

Alrighty, sounds good to me.

> 
>> +			}
>> +
>> +			if (flags&  EXT4_DEL_ENTRY_ZERO ||
>> +				flags&  EXT4_DEL_ENTRY_RAND) {
>> +
>> +				set_buffer_dirty(bh);
>> +				sync_dirty_buffer(bh);
>> +				if (buffer_req(bh)&&  !buffer_uptodate(bh)) {
>> +					es->s_last_error_block =
>> +						cpu_to_le64(bh->b_blocknr);
>> +					ext4_error_inode(dir, __func__,
>> +					   __LINE__, bh->b_blocknr,
>> +					   "IO error syncing itable block");
> 
> itable?

Sorry, I borrowed this snippet from another area of code and forgot to update the error message.  Will fix :)

> 
> --D
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