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ext4: 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>
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);