From: Kees Cook <keescook@chromium.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Kees Cook" <keescook@chromium.org>,
"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: [PATCH] x86/purgatory: Do not use fortified string functions
Date: Tue, 30 May 2023 17:33:48 -0700 [thread overview]
Message-ID: <20230531003345.never.325-kees@kernel.org> (raw)
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>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Alyssa Ross <hi@alyssa.is>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/purgatory/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 82fec66d46d2..005324d6c76b 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -12,7 +12,7 @@ $(obj)/string.o: $(srctree)/arch/x86/boot/compressed/string.c FORCE
$(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE
$(call if_changed_rule,cc_o_c)
-CFLAGS_sha256.o := -D__DISABLE_EXPORTS
+CFLAGS_sha256.o := -D__DISABLE_EXPORTS -D__NO_FORTIFY
# When linking purgatory.ro with -r unresolved symbols are not checked,
# also link a purgatory.chk binary without -r to check for unresolved symbols.
--
2.34.1
next reply other threads:[~2023-05-31 0:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-31 0:33 Kees Cook [this message]
2023-05-31 7:51 ` [PATCH] x86/purgatory: Do not use fortified string functions Thorsten Leemhuis
2023-06-01 16:45 ` Dave Hansen
2023-06-01 16:50 ` Kees Cook
2023-06-01 16:57 ` 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=20230531003345.never.325-kees@kernel.org \
--to=keescook@chromium.org \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=glider@google.com \
--cc=gustavoars@kernel.org \
--cc=hi@alyssa.is \
--cc=hpa@zytor.com \
--cc=joanbrugueram@gmail.com \
--cc=linux-hardening@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@leemhuis.info \
--cc=masahiroy@kernel.org \
--cc=mingo@redhat.com \
--cc=ndesaulniers@google.com \
--cc=peterz@infradead.org \
--cc=samitolvanen@google.com \
--cc=tglx@linutronix.de \
--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).