Re: [PATCH] powerpc/kernel: Fix potential spectre v1 in syscall

Breno Leitao [off-list ref] writes:

On Tue, Mar 12, 2024 at 08:17:42AM +0000, Christophe Leroy wrote:

quoted

+Nathan as this is RTAS related.

Le 21/08/2018 à 20:42, Breno Leitao a écrit :

quoted

The rtas syscall reads a value from a user-provided structure and uses it
to index an array, being a possible area for a potential spectre v1 attack.
This is the code that exposes this problem.

	args.rets = &args.args[nargs];

The nargs is an user provided value, and the below code is an example where
the 'nargs' value would be set to XX.

	struct rtas_args ra;
	ra.nargs = htobe32(XX);
	syscall(__NR_rtas, &ra);

This patch has been hanging around in patchwork since 2018 and doesn't 
apply anymore. Is it still relevant ? If so, can you rebase et resubmit ?

This seems to be important, since nargs is a user-provided value. I can
submit it if the maintainers are willing to accept. I do not want to
spend my time if no one is willing to review it.

My memory is that I didn't think it was actually a problem, because all
we do is memset args.rets to zero. I thought I'd talked to you on Slack
about it, but maybe I didn't.

Anyway we should probably just fix it to be safe and keep the static
checkers happy.

I'll rebase it and apply it, I'm sure you've got better things to do :)

cheers