linux-kernel - [PATCH AUTOSEL 6.12 317/486] x86/boot: Disable stack protector for early boot code

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250505223922.2682012-317-sashal@kernel.org>
Date: Mon,  5 May 2025 18:36:33 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Brian Gerst <brgerst@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Sasha Levin <sashal@...nel.org>,
	tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	x86@...nel.org,
	nikunj@....com,
	peterz@...radead.org,
	elver@...gle.com,
	dvyukov@...gle.com,
	yazen.ghannam@....com,
	masahiroy@...nel.org
Subject: [PATCH AUTOSEL 6.12 317/486] x86/boot: Disable stack protector for early boot code

From: Brian Gerst <brgerst@...il.com>

[ Upstream commit a9a76b38aaf577887103e3ebb41d70e6aa5a4b19 ]

On 64-bit, this will prevent crashes when the canary access is changed
from %gs:40 to %gs:__stack_chk_guard(%rip).  RIP-relative addresses from
the identity-mapped early boot code will target the wrong address with
zero-based percpu.  KASLR could then shift that address to an unmapped
page causing a crash on boot.

This early boot code runs well before user-space is active and does not
need stack protector enabled.

Signed-off-by: Brian Gerst <brgerst@...il.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: https://lore.kernel.org/r/20250123190747.745588-4-brgerst@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index f7918980667a3..f42c0903ef86d 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -44,6 +44,8 @@ KCOV_INSTRUMENT_unwind_orc.o				:= n
 KCOV_INSTRUMENT_unwind_frame.o				:= n
 KCOV_INSTRUMENT_unwind_guess.o				:= n
 
+CFLAGS_head32.o := -fno-stack-protector
+CFLAGS_head64.o := -fno-stack-protector
 CFLAGS_irq.o := -I $(src)/../include/asm/trace
 
 obj-y			+= head_$(BITS).o
-- 
2.39.5