linux-kernel - Re: [PATCH 20/26] ubifs: Add support for encrypted symlinks

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Message-ID: <e251d6e6-514c-84ba-60df-143b16a0b020@nod.at>
Date:   Mon, 24 Oct 2016 08:54:03 +0200
From:   Richard Weinberger <richard@....at>
To:     Eric Biggers <ebiggers@...gle.com>
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, dedekind1@...il.com,
        adrian.hunter@...el.com, tytso@....edu, jaegeuk@...nel.org,
        david@...ma-star.at, wd@...x.de, sbabic@...x.de,
        dengler@...utronix.de
Subject: Re: [PATCH 20/26] ubifs: Add support for encrypted symlinks

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