linux-kernel - Re: [PATCH 2/4] KVM: Avoid checking huge page mappings in get_dirty

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 14 Mar 2012 10:04:35 +0900
From:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
To:	Marcelo Tosatti <mtosatti@...hat.com>
Cc:	avi@...hat.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] KVM: Avoid checking huge page mappings in
 get_dirty_log()

Marcelo Tosatti <mtosatti@...hat.com> wrote:

> 
> This is a race with hugetlbfs which is not an issue ATM (it is 
> hidden by the removal of huge sptes in get_dirty).

Thank you!
I did not notice this possibility at all.

...

> It can be fixed with a preceding patch that checks whether
> slot->dirty_bitmap value changes between mapping_level and after
> mmu_lock acquision, similarly to mmu_seq. Also please add a 
> WARN_ON in mmu_set_spte if(slot->dirty_bitmap && level > 1).
> And document it clearly.

We may also be able to change the "if (slot->dirty_bitmap)" check to
use another flag so that we can delay the start of logging until
mmu_lock acquisition in kvm_set_memory_region().

Looking dirty_bitmap directly should be limited to when we are in
get_dirty functions.

	Takuya
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/