linux-kernel - Re: [PATCH 2/2] KVM MMU: fix race in invlpg code

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, 05 May 2010 15:31:07 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	KVM list <kvm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] KVM MMU: fix race in invlpg code

On 05/05/2010 03:21 PM, Xiao Guangrong wrote:
> It has race in invlpg code, like below sequences:
>
> A: hold mmu_lock and get 'sp'
> B: release mmu_lock and do other things
> C: hold mmu_lock and continue use 'sp'
>
> if other path freed 'sp' in stage B, then kernel will crash
>
> This patch checks 'sp' whether lived before use 'sp' in stage C
>
> Signed-off-by: Xiao Guangrong<xiaoguangrong@...fujitsu.com>
> ---
>   arch/x86/kvm/paging_tmpl.h |   22 ++++++++++++++++++++--
>   1 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 624b38f..13ea675 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -462,11 +462,16 @@ out_unlock:
>
>   static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
>   {
> -	struct kvm_mmu_page *sp = NULL;
> +	struct kvm_mmu_page *sp = NULL, *s;
>   	struct kvm_shadow_walk_iterator iterator;
> +	struct hlist_head *bucket;
> +	struct hlist_node *node, *tmp;
>   	gfn_t gfn = -1;
>   	u64 *sptep = NULL, gentry;
>   	int invlpg_counter, level, offset = 0, need_flush = 0;
> +	unsigned index;
> +	bool live = false;
> +	union kvm_mmu_page_role role;
>
>   	spin_lock(&vcpu->kvm->mmu_lock);
>
> @@ -480,7 +485,7 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
>
>   			if (!sp->unsync)
>   				break;
> -
> +			role = sp->role;
>   			WARN_ON(level != PT_PAGE_TABLE_LEVEL);
>   			shift = PAGE_SHIFT -
>   				  (PT_LEVEL_BITS - PT64_LEVEL_BITS) * level;
> @@ -519,10 +524,23 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva)
>
>   	mmu_guess_page_from_pte_write(vcpu, gfn_to_gpa(gfn) + offset, gentry);
>   	spin_lock(&vcpu->kvm->mmu_lock);
> +	index = kvm_page_table_hashfn(gfn);
> +	bucket =&vcpu->kvm->arch.mmu_page_hash[index];
> +	hlist_for_each_entry_safe(s, node, tmp, bucket, hash_link)
> +		if (s == sp) {
> +			if (s->gfn == gfn&&  s->role.word == role.word)
> +				live = true;
> +			break;
> +		}
> +
> +	if (!live)
> +		goto unlock_exit;
> +
>    

Did you try the root_count method?  I think it's cleaner.

-- 
error compiling committee.c: too many arguments to function

--
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/