From: Borislav Petkov <bp@alien8.de>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>, Jann Horn <jannh@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
the arch/x86 maintainers <x86@kernel.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
kasan-dev <kasan-dev@googlegroups.com>,
kernel list <linux-kernel@vger.kernel.org>,
Andrey Konovalov <andreyknvl@google.com>,
Andy Lutomirski <luto@kernel.org>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v3 2/4] x86/traps: Print non-canonical address on #GP
Date: Wed, 20 Nov 2019 18:37:22 +0100 [thread overview]
Message-ID: <20191120173722.GH2634@zn.tnic> (raw)
In-Reply-To: <20191120162143.GB32572@linux.intel.com>
On Wed, Nov 20, 2019 at 08:21:43AM -0800, Sean Christopherson wrote:
> On Wed, Nov 20, 2019 at 02:39:13PM +0100, Borislav Petkov wrote:
> > On Wed, Nov 20, 2019 at 02:28:30PM +0100, Ingo Molnar wrote:
> > > I'd rather we not trust the decoder and the execution environment so much
> > > that it never produces a 0 linear address in a #GP:
> >
> > I was just scratching my head whether I could trigger a #GP with address
> > of 0. But yeah, I agree, let's be really cautious here. I wouldn't want
> > to debug a #GP with a wrong address reported.
>
> It's definitely possible, there are a handful of non-SIMD instructions that
> generate #GP(0) it CPL=0 in 64-bit mode *and* have a memory operand. Some
> of them might even be legitimately encountered in the wild.
>
> - CMPXCHG16B if it's not supported by the CPU.
> - VMXON if CR4 is misconfigured or VMX isn't enabled in FEATURE_CONTROL.
> - MONITOR if ECX has an invalid hint (although MONITOR hardcodes the
> address in DS:RAX and so doesn't have a ModR/M byte).
>
> Undoudbtedly there are other instructions with similar sources of #GP.
Right, we currently put our trust in the insn decoder to handle those
correctly too.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2019-11-20 17:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 10:36 [PATCH v3 1/4] x86/insn-eval: Add support for 64-bit kernel mode Jann Horn
2019-11-20 10:36 ` [PATCH v3 2/4] x86/traps: Print non-canonical address on #GP Jann Horn
2019-11-20 11:18 ` Ingo Molnar
2019-11-20 11:24 ` Borislav Petkov
2019-11-20 12:25 ` Jann Horn
2019-11-20 12:41 ` Borislav Petkov
2019-11-20 13:16 ` Ingo Molnar
2019-11-20 13:23 ` Jann Horn
2019-11-20 14:05 ` Ingo Molnar
2019-11-20 12:14 ` Jann Horn
2019-11-20 12:30 ` Ingo Molnar
2019-11-20 12:39 ` Borislav Petkov
2019-11-20 12:42 ` Jann Horn
2019-11-20 13:28 ` Ingo Molnar
2019-11-20 13:39 ` Borislav Petkov
2019-11-20 16:21 ` Sean Christopherson
2019-11-20 17:37 ` Borislav Petkov [this message]
2019-11-20 10:36 ` [PATCH v3 3/4] x86/dumpstack: Split out header line printing from __die() Jann Horn
2019-11-20 10:36 ` [PATCH v3 4/4] x86/kasan: Print original address on #GP Jann Horn
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