[PATCH 0/4] CRASH_ZEROIZE: Wipe secrets before kdump

[Jan Sebastian Götte]

Hi there,

On 8/1/26 16:03, Baoquan He wrote:
> On 07/31/26 at 05:46pm, Jan Sebastian Götte wrote:
>> Add CONFIG_CRASH_ZEROIZE (default off), which when enabled makes various
>> subsystems handling secret data do a quick, targeted wipe of these
>> secrets before kdump. This behavior might also be interesting in cases
>> where you run a normal kdump kernel but you still want to keep things
>> like fde crypto keys out of these dumps.
> 
> Please check below patchset, you both seem to have the similar
> requirement. Please go there to discuss.
> 
> [RFC PATCH 0/4] panic: a pre kdump notifier list for hypervisor upcalls

Thank you for the pointer. That's indeed similar, but I think this 
patchset here makes sense as an independent patchset.

* The two notifier chains run at different points, and theirs runs 
inside panic independent of kdump. This one here has to be run after 
machine_crash_shutdown(), and so makes most sense inside 
__crash_kexec(). The wipe code in this patchset must be one of the last 
things to run before the kexec since the wiped data structures could 
easily lead to problems if something tried using them later.

* I think this patch series here is a bit cleaner. I don't think this 
needs a custom notifier implementation.

* Since there's lots of places that may need wiping after crash, I think 
it makes sense to have an explicit notifier list for that purpose, and 
to not mix these with other things like hypercalls. I think ordering is 
important here: The wiping should be the last thing before the kexec 
jump. Having it on a generic notifier chain risks that later, other 
callbacks get added that when interleaved could cause problems.

* Since a good fraction of users may not care about wiping secrets, I 
think it should be gated behind an explicit enable setting.

> Note that we usually dont' want to run a lot of work after panic and
> before jumping into kdump kernel.

I understand. For this reason, I think it's best to keep this 
default-off. As-is, the notifier list call is timed and on the (slow) 
ARM64 target I'm using, it takes about 3-5 ms to run. I took the "try 
lock, skip if locked" approach to keep the risk of this code crashing 
during panic minimal. In my application, the kdump payload is code that 
then does a full wipe, taking a couple hundred milliseconds.

Let me know what you think.