linux-kernel - Re: [PATCH v2 06/11] KVM: x86: emulator/smm: number of GPRs in the SMRAM image depends on the image format

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: <YtiZNg7LqVuepc85@google.com>
Date:   Thu, 21 Jul 2022 00:09:26 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH v2 06/11] KVM: x86: emulator/smm: number of GPRs in the
 SMRAM image depends on the image format

On Thu, Jul 21, 2022, Sean Christopherson wrote:
> On Tue, Jun 21, 2022, Maxim Levitsky wrote:
> > On 64 bit host, if the guest doesn't have X86_FEATURE_LM, we would
> 
> s/we would/KVM will
> 
> > access 16 gprs to 32-bit smram image, causing out-ouf-bound ram
> > access.
> > 
> > On 32 bit host, the rsm_load_state_64/enter_smm_save_state_64
> > is compiled out, thus access overflow can't happen.
> > 
> > Fixes: b443183a25ab61 ("KVM: x86: Reduce the number of emulator GPRs to '8' for 32-bit KVM")
> 
> Argh, I forgot that this one of the like five places KVM actually respects the
> long mode flag.  Even worse, I fixed basically the same thing a while back,
> commit b68f3cc7d978 ("KVM: x86: Always use 32-bit SMRAM save state for 32-bit kernels").
> 
> We should really harden put_smstate() and GET_SMSTATE()...

Or I could read the next few patches and see that they go away...