From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Robert Gill <rtgill82@gmail.com>,
Jari Ruusu <jariruusu@protonmail.com>,
Brian Gerst <brgerst@gmail.com>,
"Linux regression tracking (Thorsten Leemhuis)"
<regressions@leemhuis.info>,
antonio.gomez.iglesias@linux.intel.com,
daniel.sneddon@linux.intel.com
Subject: Re: [PATCH v6 1/3] x86/entry_32: Do not clobber user EFLAGS.ZF
Date: Fri, 13 Sep 2024 12:10:22 -0700 [thread overview]
Message-ID: <20240913191022.fqipwsazkkrm5x67@desk> (raw)
In-Reply-To: <cd2897c7-2479-4358-bd5e-b55ec84db2ce@intel.com>
On Thu, Sep 12, 2024 at 10:45:23AM -0700, Dave Hansen wrote:
> On 9/5/24 09:00, Pawan Gupta wrote:
> > Opportunistic SYSEXIT executes VERW to clear CPU buffers after user EFLAGS
> > are restored. This can clobber user EFLAGS.ZF.
> >
> > Move CLEAR_CPU_BUFFERS before the user EFLAGS are restored. This ensures
> > that the user EFLAGS.ZF is not clobbered.
>
> Just to be clear, the new (later) location is also safe for RFDS because
> it only exposes the contents of EFLAGS (not sensitive) and RAX.
Right.
> RAX might leak the old or new values of CR3, which do not seem super
> valuable to me.
>
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Thanks.
next prev parent reply other threads:[~2024-09-13 19:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-05 16:00 [PATCH v6 0/3] Fix dosemu vm86() fault Pawan Gupta
2024-09-05 16:00 ` [PATCH v6 1/3] x86/entry_32: Do not clobber user EFLAGS.ZF Pawan Gupta
2024-09-12 17:45 ` Dave Hansen
2024-09-13 19:10 ` Pawan Gupta [this message]
2024-09-05 16:00 ` [PATCH v6 2/3] x86/entry_32: Clear CPU buffers after register restore in NMI return Pawan Gupta
2024-09-12 17:39 ` Dave Hansen
2024-09-05 16:00 ` [PATCH v6 3/3] x86/bugs: Use stack segment selector for VERW operand Pawan Gupta
2024-09-25 21:11 ` Pawan Gupta
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