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ext4: require key for truncate(2) of encrypted file

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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>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Eric Biggers 2017-06-23 19:48:44 -04:00 committed by Theodore Ts'o
parent 66e0aaadce
commit 63136858ae
1 changed files with 8 additions and 0 deletions
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8
fs/ext4/inode.c
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@ -5323,6 +5323,14 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
loff_t oldsize = inode->i_size;
int shrink = (attr->ia_size <= inode->i_size);
if (ext4_encrypted_inode(inode)) {
error = fscrypt_get_encryption_info(inode);
if (error)
return error;
if (!fscrypt_has_encryption_key(inode))
return -ENOKEY;
}
if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);