linux-ext4 - Re: [f2fs-dev] [PATCH 2/3] f2fs: require key for truncate(2) of encrypted file

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Message-ID: <e558657c-d383-4528-9be0-8c2d1ab8344c@kernel.org>
Date:   Wed, 14 Jun 2017 20:44:19 +0800
From:   Chao Yu <chao@...nel.org>
To:     Eric Biggers <ebiggers3@...il.com>, linux-fscrypt@...r.kernel.org
Cc:     Theodore Ts'o <tytso@....edu>, Eric Biggers <ebiggers@...gle.com>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-mtd@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH 2/3] f2fs: require key for truncate(2) of
 encrypted file

On 2017/6/14 7:47, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> Currently, filesystems allow truncate(2) on an encrypted file without
> the encryption key.  However, it's impossible to correctly handle the
> case where the size being truncated to is not a multiple of the
> filesystem block size, because that would require decrypting the final
> block, zeroing the part beyond i_size, then encrypting the block.
> 
> As other modifications to encrypted file contents are prohibited without
> the key, just prohibit truncate(2) as well, making it fail with ENOKEY.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Acked-by: Chao Yu <yuchao0@...wei.com>

Thanks,