[ath9k-devel] [PATCH v2] RANDOM: ATH9K RNG delivers zero bits of entropy

[Kalle Valo]

The entropy was evaluated by crypto expert, the analysis report show
the ADC with at least 10bits and up to 22 bits of min-entropy for a 32
bits value, we conservatively assume the min-entropy is 10 bits out of
32 bits, so that's why set entropy quality to 320/1024 = 10/32. Also
we have explained in the commit message why can't use the HW RNG
framework.
Otherwise, your patch will cause high CPU load, as continuously read
ADC data if entropy bits under write_wakeup_threshold.

Please don't top post, it breaks patchwork which is extremely annoying
for me:

https://patchwork.kernel.org/patch/9266265/

https://patchwork.kernel.org/patch/9266617/

[Kalle Valo]

The ATH9K driver implements an RNG which is completely bypassing the
standard Linux HW generator logic.
The RNG may or may not deliver entropy. Considering the conservative
approach in treating entropy with respect to non-auditable sources, this
patch changes the delivered entropy value to zero. The RNG still feeds
data into the input_pool but it is assumed to have no entropy.
When the ATH9K RNG changes to use the HW RNG framework, it may re-enable
the entropy estimation considering that a user can change that value at
boot and runtime.

Based on the discussion I'm dropping this patch. But the discussion was
hard to follow so please let me know if I misunderstood.

Patch set to Rejected.