Re: [PATCH v2 0/2] block: Use 'read-zeroes=true' mode by default with 'null-co' driver

[Max Reitz]

On 13.02.21 22:54, Fam Zheng wrote:
> On 2021-02-11 15:26, Philippe Mathieu-Daudé wrote:
> > The null-co driver doesn't zeroize buffer in its default config,
> > because it is designed for testing and tests want to run fast.
> > However this confuses security researchers (access to uninit
> > buffers).
>
> I'm a little surprised.
>
> Is changing default the only way to fix this? I'm not opposed to
> changing the default but I'm not convinced this is the easiest way.
> block/nvme.c also doesn't touch the memory, but defers to the device
> DMA, why doesn't that confuse the security checker?
>
> Cannot we just somehow annotate it in a way that the checker can
> understand (akin to how we provide coverity models) and be done?

The question is, why wouldn’t we change the default?  read-zeroes=true 
seems the better default to me.  I consider silencing valgrind warnings 
and the like a nice side effect.

Max