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If > you take a look at the function that reads data from the iov_iter: > > static int fill_write_buffer(struct configfs_buffer *buffer, > struct iov_iter *from) > { > int copied; > > if (!buffer->page) > buffer->page =3D kmalloc(PAGE_SIZE, GFP_KERNEL); // <- HERE > if (!buffer->page) > return -ENOMEM; > > copied =3D copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from); > buffer->needs_read_fill =3D 1; > /* if buf is assumed to contain a string, terminate it by \0, > * so e.g. sscanf() can scan the string easily */ > buffer->page[copied] =3D 0; > return copied ? : -EFAULT; > } > > This function does not zero the page that is written into. This, > combined with the buffer being per file handle means that you can read > the original data in the page. The `kmalloc` should be probably be > replaced with a `kzalloc`. This should be a problem for C modules as > well. Why is this an issue? The extra uninitialized bytes should not be used. Best, Gary > > Cc: Breno Leitao > > Looks like I only replied Priya when replying, so I'm adding back > everyone from the original email. > > Best regards, > Andreas Hindborg