f2fs: require key for truncate(2) of encrypted file
authorEric Biggers <ebiggers@google.com>
Tue, 13 Jun 2017 23:47:54 +0000 (16:47 -0700)
committerJaegeuk Kim <jaegeuk@kernel.org>
Tue, 4 Jul 2017 09:11:46 +0000 (02:11 -0700)
commit67773a1fbdcb5be4a0490b1dd2a5975784ef40df
treece3d823e454f55d2c638e99d0a12ccd63469fbf0
parent8ceffcb29e61ba882a011b1e4d73ca03691fdc2e
f2fs: require key for truncate(2) of encrypted file

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@google.com>
Acked-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
fs/f2fs/file.c