From: Dave Hansen <dave.hansen@intel.com>
To: Kees Cook <keescook@chromium.org>, Thomas Gleixner <tglx@linutronix.de>
Cc: "Thorsten Leemhuis" <linux@leemhuis.info>,
"Joan Bruguera Micó" <joanbrugueram@gmail.com>,
"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>,
"Nick Desaulniers" <ndesaulniers@google.com>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
"Alyssa Ross" <hi@alyssa.is>,
"Sami Tolvanen" <samitolvanen@google.com>,
"Alexander Potapenko" <glider@google.com>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] x86/purgatory: Do not use fortified string functions
Date: Thu, 1 Jun 2023 09:45:57 -0700 [thread overview]
Message-ID: <3c67fdd6-bce9-f695-a6c5-0fe9209bd3e4@intel.com> (raw)
In-Reply-To: <20230531003345.never.325-kees@kernel.org>
On 5/30/23 17:33, Kees Cook wrote:
> With the addition of -fstrict-flex-arrays=3, struct sha256_state's
> trailing array is no longer ignored by CONFIG_FORTIFY_SOURCE:
>
> struct sha256_state {
> u32 state[SHA256_DIGEST_SIZE / 4];
> u64 count;
> u8 buf[SHA256_BLOCK_SIZE];
> };
>
> This means that the memcpy() calls with "buf" as a destination in
> sha256.c's code will attempt to perform run-time bounds checking, which
> could lead to calling missing functions, specifically a potential
> WARN_ONCE, which isn't callable from purgatory.
>
> Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
> Closes: https://lore.kernel.org/lkml/175578ec-9dec-7a9c-8d3a-43f24ff86b92@leemhuis.info/
> Bisected-by: "Joan Bruguera Micó" <joanbrugueram@gmail.com>
> Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3")
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
Hi Folks,
The -fstrict-flex-arrays=3 commit isn't upstream yet, right? That makes
it a _bit_ wonky for us to carry this on the x86 side since among other
things, the Fixes commit doesn't exist. I'd be fine if this goes up
along with the -fstrict-flex-arrays=3 code, so:
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
We could also pick it up from the x86 side, but I think that would need
a _bit_ of a different commit message to allude to it being to prepare
for the _future_ setting of -fstrict-flex-arrays=3 and having no
practical benefits now.
Let me know if you don't want to send this up with the
-fstrict-flex-arrays=3 set.
next prev parent reply other threads:[~2023-06-01 16:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-31 0:33 [PATCH] x86/purgatory: Do not use fortified string functions Kees Cook
2023-05-31 7:51 ` Thorsten Leemhuis
2023-06-01 16:45 ` Dave Hansen [this message]
2023-06-01 16:50 ` Kees Cook
2023-06-01 16:57 ` Kees Cook
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