From: Thomas Gleixner <tglx@linutronix.de>
To: Kees Cook <keescook@chromium.org>
Cc: Kees Cook <keescook@chromium.org>,
Elena Reshetova <elena.reshetova@intel.com>,
x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Potapenko <glider@google.com>,
Alexander Popov <alex.popov@linux.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Jann Horn <jannh@google.com>, Vlastimil Babka <vbabka@suse.cz>,
David Hildenbrand <david@redhat.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jonathan Corbet <corbet@lwn.net>,
Randy Dunlap <rdunlap@infradead.org>,
kernel-hardening@lists.openwall.com,
linux-hardening@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 4/6] x86/entry: Enable random_kstack_offset support
Date: Sun, 28 Mar 2021 16:18:56 +0200 [thread overview]
Message-ID: <87h7kvcqen.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20210319212835.3928492-5-keescook@chromium.org>
On Fri, Mar 19 2021 at 14:28, Kees Cook wrote:
> +
> + /*
> + * x86_64 stack alignment means 3 bits are ignored, so keep
> + * the top 5 bits. x86_32 needs only 2 bits of alignment, so
> + * the top 6 bits will be used.
> + */
> + choose_random_kstack_offset(rdtsc() & 0xFF);
Comment mumbles about 5/6 bits and the TSC value is masked with 0xFF and
then the applied offset is itself limited with 0x3FF.
Too many moving parts for someone who does not have the details of all
this memorized.
Thanks,
tglx
next prev parent reply other threads:[~2021-03-28 14:20 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 21:28 [PATCH v7 0/6] Optionally randomize kernel stack offset each syscall Kees Cook
2021-03-19 21:28 ` [PATCH v7 1/6] jump_label: Provide CONFIG-driven build state defaults Kees Cook
2021-03-19 21:28 ` [PATCH v7 2/6] init_on_alloc: Optimize static branches Kees Cook
2021-03-19 21:28 ` [PATCH v7 3/6] stack: Optionally randomize kernel stack offset each syscall Kees Cook
2021-03-28 14:42 ` Thomas Gleixner
2021-03-29 18:41 ` Kees Cook
2021-03-19 21:28 ` [PATCH v7 4/6] x86/entry: Enable random_kstack_offset support Kees Cook
2021-03-20 11:58 ` Ingo Molnar
2021-03-21 17:03 ` Kees Cook
2021-03-28 14:18 ` Thomas Gleixner [this message]
2021-03-29 18:43 ` Kees Cook
2021-03-19 21:28 ` [PATCH v7 5/6] arm64: entry: " Kees Cook
2021-04-01 8:34 ` Will Deacon
2021-03-19 21:28 ` [PATCH v7 6/6] lkdtm: Add REPORT_STACK for checking stack offsets Kees Cook
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=87h7kvcqen.ffs@nanos.tec.linutronix.de \
--to=tglx@linutronix.de \
--cc=akpm@linux-foundation.org \
--cc=alex.popov@linux.com \
--cc=ard.biesheuvel@linaro.org \
--cc=catalin.marinas@arm.com \
--cc=corbet@lwn.net \
--cc=david@redhat.com \
--cc=elena.reshetova@intel.com \
--cc=glider@google.com \
--cc=jannh@google.com \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mark.rutland@arm.com \
--cc=peterz@infradead.org \
--cc=rdunlap@infradead.org \
--cc=rppt@linux.ibm.com \
--cc=vbabka@suse.cz \
--cc=will@kernel.org \
--cc=x86@kernel.org \
/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;
as well as URLs for NNTP newsgroup(s).