From: Kees Cook <keescook@chromium.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, Sami Tolvanen <samitolvanen@google.com>,
Joao Moreira <joao@overdrivepizza.com>,
linux-kernel@vger.kernel.org, Mark Rutland <mark.rutland@arm.com>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH] x86/ibt: Implement FineIBT
Date: Tue, 18 Oct 2022 22:05:26 -0700 [thread overview]
Message-ID: <202210182200.50680AE@keescook> (raw)
In-Reply-To: <Y08FhjK3fKsfRAaw@hirez.programming.kicks-ass.net>
On Tue, Oct 18, 2022 at 09:59:02PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 18, 2022 at 11:09:13AM -0700, Kees Cook wrote:
>
> > An improvement for kCFI would be to mutate all the hashes both at build
> > time (perhaps using the same seed infrastructure that randstruct depends
> > on for sharing a seed across compilation units), and at boot time, so
> > an actual .text content exposure is needed to find the target hash value.
>
> What's the purpose of the build time randomization?
I was just considering options if run-time was too onerous.
> Find here the boot
> time randomization (on top of my other patch).
Which it's clearly not. :P Nice!
> [...]
> static enum cfi_mode cfi_mode __ro_after_init = CFI_DEFAULT;
> +static bool cfi_rand __ro_after_init = true;
> +static u32 cfi_seed __ro_after_init;
This is saved because we need to fix up modules, yes? I look forward
to fine-grain randomization of the .data section. ;)
> [...]
> +static int cfi_rand_preamble(s32 *start, s32 *end)
> +{
> + s32 *s;
> +
> + for (s = start; s < end; s++) {
> + void *addr = (void *)s + *s;
> + u32 hash;
> +
> + hash = decode_preamble_hash(addr);
> + if (WARN(!hash, "no CFI hash found at: %pS %px %*ph\n",
> + addr, addr, 5, addr))
> + return -EINVAL;
> +
> + hash ^= cfi_seed;
> + text_poke_early(addr + 1, &hash, 4);
> + }
> +
> + return 0;
> +}
The one glitch here is that the resulting hash needs to not contain
an endbr...
Otherwise, yes, this looks lovely. Thank you!
--
Kees Cook
next prev parent reply other threads:[~2022-10-19 5:05 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-18 13:35 [PATCH] x86/ibt: Implement FineIBT Peter Zijlstra
2022-10-18 14:43 ` David Laight
2022-10-18 15:58 ` Joao Moreira
2022-10-18 17:20 ` Kees Cook
2022-10-18 20:09 ` Joao Moreira
2022-10-19 5:33 ` Kees Cook
2022-10-18 21:27 ` David Laight
2022-10-18 14:47 ` Peter Zijlstra
2022-10-18 18:09 ` Kees Cook
2022-10-18 19:56 ` Peter Zijlstra
2022-10-18 23:31 ` Josh Poimboeuf
2022-10-19 5:22 ` Kees Cook
2022-10-19 11:38 ` Peter Zijlstra
2022-10-19 5:14 ` Kees Cook
2022-10-18 19:59 ` Peter Zijlstra
2022-10-18 21:09 ` Peter Zijlstra
2022-10-19 5:05 ` Kees Cook [this message]
2022-10-19 12:03 ` Peter Zijlstra
2022-10-19 15:22 ` Sami Tolvanen
2022-10-20 11:04 ` Peter Zijlstra
2022-10-18 19:59 ` Joao Moreira
2022-10-19 5:32 ` Kees Cook
2022-10-19 19:35 ` Joao Moreira
2022-10-18 20:05 ` Peter Zijlstra
2022-10-19 5:00 ` Kees Cook
2022-10-18 20:09 ` Peter Zijlstra
2022-10-18 20:17 ` Joao Moreira
2022-10-18 20:30 ` Peter Zijlstra
2022-10-19 4:48 ` Joao Moreira
2022-10-19 5:19 ` Kees Cook
2022-10-31 19:13 ` Joao Moreira
2022-11-01 21:39 ` Kees Cook
2022-11-01 21:50 ` Joao Moreira
2024-05-06 17:36 ` Kees Cook
2024-05-07 1:45 ` Joao Moreira
2022-10-19 5:18 ` Kees Cook
2022-10-19 5:16 ` Kees Cook
2022-10-20 11:05 ` Peter Zijlstra
2022-10-18 23:38 ` Josh Poimboeuf
2022-10-19 7:29 ` Peter Zijlstra
2022-10-21 23:08 ` Josh Poimboeuf
2022-10-22 15:03 ` Peter Zijlstra
2022-10-24 17:15 ` Sami Tolvanen
2022-10-24 18:38 ` Joao Moreira
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