From: Kees Cook <keescook@chromium.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Robert Dinse <nanook@eskimo.com>
Subject: Re: [PATCH 1/4] KVM: x86: Grab regs_dirty in local 'unsigned long'
Date: Thu, 26 May 2022 08:33:03 -0700 [thread overview]
Message-ID: <202205260832.0301216FB6@keescook> (raw)
In-Reply-To: <20220525222604.2810054-2-seanjc@google.com>
On Wed, May 25, 2022 at 10:26:01PM +0000, Sean Christopherson wrote:
> Capture ctxt->regs_dirty in a local 'unsigned long' instead of casting
> ctxt->regs_dirty to an 'unsigned long *' for use in for_each_set_bit().
> The bitops helpers really do read the entire 'unsigned long', even though
> the walking of the read value is capped at the specified size. I.e. KVM
> is reading memory beyond ctxt->regs_dirty. Functionally it's not an
> issue because regs_dirty is in the middle of x86_emulate_ctxt, i.e. KVM
> is just reading its own memory, but relying on that coincidence is gross
> and unsafe.
Right; there have bean a handful of other bitops-using-stuff-cast-to-ulong
that has been recently fixed elsewhere. Better to get them all squashed.
:)
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
next prev parent reply other threads:[~2022-05-26 15:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-25 22:26 [PATCH 0/4] KVM: x86: Emulator _regs fixes and cleanups Sean Christopherson
2022-05-25 22:26 ` [PATCH 1/4] KVM: x86: Grab regs_dirty in local 'unsigned long' Sean Christopherson
2022-05-26 14:04 ` Vitaly Kuznetsov
2022-05-26 15:33 ` Kees Cook [this message]
2022-05-25 22:26 ` [PATCH 2/4] KVM: x86: Harden _regs accesses to guard against buggy input Sean Christopherson
2022-05-26 14:07 ` Vitaly Kuznetsov
2022-05-26 15:49 ` Sean Christopherson
2022-05-26 15:58 ` Vitaly Kuznetsov
2022-05-26 15:39 ` Kees Cook
2022-05-26 16:01 ` Sean Christopherson
2022-05-25 22:26 ` [PATCH 3/4] KVM: x86: Omit VCPU_REGS_RIP from emulator's _regs array Sean Christopherson
2022-05-26 2:55 ` kernel test robot
2022-05-26 15:47 ` Sean Christopherson
2022-05-25 22:26 ` [PATCH 4/4] KVM: x86: Use 16-bit fields to track dirty/valid emulator GPRs Sean Christopherson
2022-05-26 15:41 ` Kees Cook
2022-05-26 1:48 ` [PATCH 0/4] KVM: x86: Emulator _regs fixes and cleanups Robert Dinse
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