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]
Message-ID: <20120112101259.GW2167@redhat.com>
Date:	Thu, 12 Jan 2012 12:12:59 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Nadav Amit <namit@...technion.ac.il>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Nadav Amit <nadav.amit@...il.com>
Subject: Re: [PATCH 2/2] KVM: Fix writeback on page boundary that propagate
 changes in spite of #PF

On Wed, Jan 11, 2012 at 06:53:31PM +0200, Nadav Amit wrote:
> Consider the case in which an instruction emulation writeback is performed on a page boundary.
> In such case, if a #PF occurs on the second page, the write to the first page already occurred and cannot be retracted.
> Therefore, validation of the second page access must be performed prior to writeback.
> 
> Signed-off-by: Nadav Amit <nadav.amit@...il.com>
> ---
>  arch/x86/kvm/x86.c |   13 +++++++++++++
>  1 files changed, 13 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 05fd3d7..7af3d67 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3626,6 +3626,8 @@ struct read_write_emulator_ops {
>  			       int bytes, void *val);
>  	int (*read_write_exit_mmio)(struct kvm_vcpu *vcpu, gpa_t gpa,
>  				    void *val, int bytes);
> +	gpa_t (*read_write_validate)(struct kvm_vcpu *vcpu, gva_t gva,
> +				     struct x86_exception *exception);
>  	bool write;
>  };
>  
> @@ -3686,6 +3688,7 @@ static struct read_write_emulator_ops write_emultor = {
>  	.read_write_emulate = write_emulate,
>  	.read_write_mmio = write_mmio,
>  	.read_write_exit_mmio = write_exit_mmio,
> +	.read_write_validate = kvm_mmu_gva_to_gpa_write,
>  	.write = true,
>  };
>  
> @@ -3750,6 +3753,16 @@ int emulator_read_write(struct x86_emulate_ctxt *ctxt, unsigned long addr,
>  		int rc, now;
>  
>  		now = -addr & ~PAGE_MASK;
> +
> +		/* First check there is no page-fault on the next page */
> +		if (ops->read_write_validate &&
> +			ops->read_write_validate(vcpu, addr+now, exception) ==
> +			UNMAPPED_GVA) {
> +			/* #PF on the first page should be reported first */
> +			ops->read_write_validate(vcpu, addr, exception);
> +			return X86EMUL_PROPAGATE_FAULT;
> +		}
> +
This undoes optimization that vcpu_mmio_gva_to_gpa() has for handling
mmio. Furthermore for common (non faulting) case we will check page
tables twice on each write that crosses page boundary, first time here
and second time in emulator_read_write_onepage().

>  		rc = emulator_read_write_onepage(addr, val, now, exception,
>  						 vcpu, ops);
>  
> -- 
> 1.7.4.1
> 
> --
> 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/

--
			Gleb.
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ