Re: null_handle_cmd() doesn't initialize data when reading

On 2020-05-11 18:42, Damien Le Moal wrote:

The patch looks good to me. However, I have one concern regarding the
performance impact of this. When nullblk is used to benchmark the block IO stack
overhead, doing this zeroing unconditionally will likely significantly impact
measured performance. So may be this zeroing feature should be driven by a
modprobe/configfs option ? Doing so, we can keep it off by default, preserving
performance, and turn it on when needed as in Alexander use case.

Thoughts ?

Hi Damien,

Does the current implementation of null_blk allow one process to access
data that was generated by another process? If so, does that behavior
count as a security bug?

I am aware of the performance impact of the patch attached to my
previous email. I have not made the zeroing behavior optional because
I'm concerned about the security implications of doing that.

Bart.