From: Ingo Molnar <mingo@kernel.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
Fei Yang <fei.yang@intel.com>,
stable@vger.kernel.org
Subject: Re: [PATCHv2] x86/alternatives: Disable KASAN in apply_alternatives()
Date: Wed, 11 Oct 2023 22:45:27 +0200 [thread overview]
Message-ID: <ZScJZ7Uc6aJNyvRg@gmail.com> (raw)
In-Reply-To: <20231011132703.3evo4ieradgyvgc2@box.shutemov.name>
* Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote:
> On Wed, Oct 11, 2023 at 09:46:16AM +0200, Peter Zijlstra wrote:
> > On Wed, Oct 11, 2023 at 09:58:49AM +0300, Kirill A. Shutemov wrote:
> > > Fei has reported that KASAN triggers during apply_alternatives() on
> > > 5-level paging machine:
> > >
> >
> > Urgh @ KASAN splat, can't we summarize that?
>
> What about this?
>
> BUG: KASAN: out-of-bounds in rcu_is_watching
> Read of size 4 at addr ff110003ee6419a0 by task swapper/0/0
> ...
> __asan_load4
> rcu_is_watching
> ? text_poke_early
> trace_hardirqs_on
> ? __asan_load4
> text_poke_early
> apply_alternatives
> ...
>
> Is it enough details or I overdid summarization?
No, that's perfect IMO. I'd even leave out the unreliable '?' entries:
> BUG: KASAN: out-of-bounds in rcu_is_watching
> Read of size 4 at addr ff110003ee6419a0 by task swapper/0/0
> ...
> __asan_load4
> rcu_is_watching
> trace_hardirqs_on
> text_poke_early
> apply_alternatives
> ...
... or so.
> /*
> * In the case CONFIG_X86_5LEVEL=y, KASAN_SHADOW_START is defined using
> * cpu_feature_enabled(X86_FEATURE_LA57) and is therefore patched here.
> * During the process, KASAN becomes confused seeing partial LA57
> * conversion and triggers a false-positive out-of-bound report.
> *
> * Disable KASAN until the patching is complete.
> */
>
> Looks good?
LGTM.
Thanks,
Ingo
prev parent reply other threads:[~2023-10-11 20:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-11 6:58 [PATCHv2] x86/alternatives: Disable KASAN in apply_alternatives() Kirill A. Shutemov
2023-10-11 7:46 ` Peter Zijlstra
2023-10-11 8:11 ` Ingo Molnar
2023-10-11 9:37 ` Peter Zijlstra
2023-10-11 13:27 ` Kirill A. Shutemov
2023-10-11 20:45 ` Ingo Molnar [this message]
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