From: Wei Liu <wei.liu2@citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Wei Liu <wei.liu2@citrix.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Jan Beulich <JBeulich@suse.com>,
Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH for-4.8] x86/svm: Don't clobber eax and edx if an RDMSR intercept fails
Date: Thu, 10 Nov 2016 14:20:05 +0000 [thread overview]
Message-ID: <20161110142005.GE31926@citrix.com> (raw)
In-Reply-To: <1478694507-26060-1-git-send-email-andrew.cooper3@citrix.com>
On Wed, Nov 09, 2016 at 12:28:27PM +0000, Andrew Cooper wrote:
> The original code has a bug; eax and edx get unconditionally updated even when
> hvm_msr_read_intercept() doesn't return X86EMUL_OKAY.
>
> It is only by blind luck (vmce_rdmsr() eagerly initialising its msr_content
> pointer) that this isn't an information leak into guests.
>
> While fixing this bug, reduce the scope of msr_content and initialise it to 0.
> This makes it obvious that a stack leak won't occur, even if there were to be
> a buggy codepath in hvm_msr_read_intercept().
>
> Also make some non-functional improvements. Make the insn_len calculation
> common, and reduce the quantity of explicit casting by making better use of
> the existing register names.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
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prev parent reply other threads:[~2016-11-10 14:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-09 12:28 [PATCH for-4.8] x86/svm: Don't clobber eax and edx if an RDMSR intercept fails Andrew Cooper
2016-11-09 14:14 ` Jan Beulich
2016-11-09 17:43 ` Andrew Cooper
2016-11-09 16:10 ` Boris Ostrovsky
2016-11-10 14:20 ` Wei Liu [this message]
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