Re: [PATCH 3/3] x86/MCE/AMD: Get address from already initialized block

Borislav Petkov
2018-05-16T22:47:01Z

On Tue, May 15, 2018 at 11:39:54AM +0200, Johannes Hirte wrote:
> The out-of-bound access happens in get_block_address:
>
> if (bankp && bankp->blocks) {
> struct threshold_block *blockp blockp = &bankp->blocks[block];
>
> with block=1. This doesn't exists. I don't even find any array here.
> There is a linked list, created in allocate_threshold_blocks. On my
> system I get 17 lists with one element each.

Yes, what a mess this is. ;-\

There's no such thing as ->blocks[block] array. We assign simply the
threshold_block to it in allocate_threshold_blocks:

per_cpu(threshold_banks, cpu)[bank]->blocks = b;

And I can't say the design of this thing is really friendly but it is
still no excuse that I missed that during review. Grrr.

So, Yazen, what really needs to happen here is to iterate the
bank->blocks->miscj list to find the block you're looking for and return
its address, the opposite to this here:

if (per_cpu(threshold_banks, cpu)[bank]->blocks) {
list_add(&b->miscj,
&per_cpu(threshold_banks, cpu)[bank]->blocks->miscj);
} else {
per_cpu(threshold_banks, cpu)[bank]->blocks = b;
}

and don't forget to look at ->blocks itself.

And then you need to make sure that searching for block addresses still
works when resuming from suspend so that you can avoid the RDMSR IPIs.

Ok?

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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