filesystem encryption problem.

[Amir Hezarkhani]

hello
I am working on adding a simple encryption to file contents in ext4 driver
(for learning purposes) I added simple XOR encryption to aio_read and
aio_write functions and it worked until I faced this problem:

when I open a file in encrypted filesystem using VIM text editor and when I
try to save it it gives me this error:

>>pointer block id wrong
>>can not find line 1

and it just corrupts the entire file!

this is my aio_write function:

aio_write_enc(struct kiocb *iocb, const struct iovec *iov,
        unsigned long nr_segs, loff_t pos)
{
    size_t i;
    ssize_t ret;
    char *data=vmalloc(sizeof(char)*iov->iov_len);
    copy_from_user(data,iov->iov_base,iov->iov_len);

    for(i=0;i<iov->iov_len;i++)
    {
        data[i]^=5;
    }
    struct iovec iov_enc= { .iov_base = iov->iov_base, .iov_len =
iov->iov_len };

    copy_to_user(iov_enc.iov_base,data,iov->iov_len);
    ret=ext4_file_write(iocb,&iov_enc,nr_segs,pos);
    vfree(data);
    return ret;
}

this just changes the data and then calls original function.

is there anything wrong with this function? can anyone help me?
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