Subject: Re: [PATCH 20/26] ubifs: Add support for encrypted symlinks
To: Eric Biggers <ebiggers@google.com>
References: <1477054121-10198-1-git-send-email-richard@nod.at>
 <1477054121-10198-21-git-send-email-richard@nod.at>
 <20161021184231.GD90712@google.com>
Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, dedekind1@gmail.com,
        adrian.hunter@intel.com, tytso@mit.edu, jaegeuk@kernel.org,
        david@sigma-star.at, wd@denx.de, sbabic@denx.de, dengler@linutronix.de
From: Richard Weinberger <richard@nod.at>
Message-ID: <e251d6e6-514c-84ba-60df-143b16a0b020@nod.at>
Date: Mon, 24 Oct 2016 08:54:03 +0200
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Eric,

On 21.10.2016 20:42, Eric Biggers wrote:
> On Fri, Oct 21, 2016 at 02:48:35PM +0200, Richard Weinberger wrote:
>> +
>> +	if (!dentry)
>> +		return ERR_PTR(-ECHILD);
>> +
>> +	if (ubifs_crypt_is_encrypted(inode)) {
>> +		err = fscrypt_get_encryption_info(inode);
>> +		if (err)
>> +			return ERR_PTR(err);
>> +	} else
>> +		return ui->data;
>> +
> 
> This will make path lookups drop out of RCU mode when an unencrypted symlink is
> followed.  This can be avoided by checking for unencrypted symlinks first:

Oh! Thanks for pointing this out!

> 	if (!ubifs_crypt_is_encrypted(inode))
> 		return ui->data;
> 
> 	if (!dentry)
> 		return ERR_PTR(-ECHILD);
> 
> 	err = fscrypt_get_encryption_info(inode);
> 	if (err)
> 		return ERR_PTR(err);
> 
>> +
>> +	pstr.name[err] = '\0';
>> +
> 
> In 4.9, fscrypt_fname_{disk_to_usr,usr_to_disk} return 0 instead of the output
> length, so this will need to be changed to 'pstr.name[pstr.len] = '\0''.

Noted.

Thanks,
//richard