From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
LKML <linux-kernel@vger.kernel.org>, Xin Li <xin@zytor.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.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
Subject: Re: [PATCH] x86/fred: Correct speculative safety in fred_extint()
Date: Tue, 6 Jan 2026 16:46:41 +0000 [thread overview]
Message-ID: <3f9765e1-8f02-409f-813c-24ff378f7a90@citrix.com> (raw)
In-Reply-To: <20260106152008.GZ3707891@noisy.programming.kicks-ass.net>
On 06/01/2026 3:20 pm, Peter Zijlstra wrote:
> On Tue, Jan 06, 2026 at 01:15:04PM +0000, Andrew Cooper wrote:
>> This is why we have array_access_nospec() in Xen, so you can't separate the
>> safety calculation from the array access.
>>
>> The observant reader might notice that the result of reading sysvec_table[] is
>> also subject to memory predictions. Aren't CPUs wonderful...
>>
>> In practice, even having array_index_nospec() part of the array access
>> expression is no guarantee of avoiding spilling to the stack. KASAN is liable
>> to hide a function call behind the scenes, while UBSAN is very good at
>> inserting it's own unsafe range checks around objects it knows the size of.
>> Aren't compilers wonderful...
> Yeah, then again nobody should be running *SAN kernels in production,
> right ;-)
Aren't distros wonderful...
~Andrew
next prev parent reply other threads:[~2026-01-06 16:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-06 13:15 Andrew Cooper
2026-01-06 15:20 ` Peter Zijlstra
2026-01-06 16:46 ` Andrew Cooper [this message]
2026-01-06 17:06 ` H. Peter Anvin
2026-01-07 0:15 ` Andrew Cooper
2026-02-23 10:25 ` [tip: x86/urgent] " tip-bot2 for Andrew Cooper
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3f9765e1-8f02-409f-813c-24ff378f7a90@citrix.com \
--to=andrew.cooper3@citrix.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
--cc=xin@zytor.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®