linux-kernel - [PATCH v5 03/12] x86_64: load_percpu_segment: read irq_stack_union.gs_base before load

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: <1414428419-17860-4-git-send-email-a.ryabinin@samsung.com>
Date:	Mon, 27 Oct 2014 19:46:50 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andrey Ryabinin <a.ryabinin@...sung.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Konstantin Serebryany <kcc@...gle.com>,
	Dmitry Chernenkov <dmitryc@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Dave Jones <davej@...hat.com>,
	x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: [PATCH v5 03/12] x86_64: load_percpu_segment: read
 irq_stack_union.gs_base before load_segment

Reading irq_stack_union.gs_base after load_segment creates troubles for kasan.
Compiler inserts __asan_load in between load_segment and wrmsrl. If kernel
built with stackprotector this will result in boot failure because __asan_load
has stackprotector.

To avoid this irq_stack_union.gs_base stored to temporary variable before
load_segment, so __asan_load will be called before load_segment().

There are two alternative ways to fix this:
 a) Add __attribute__((no_sanitize_address)) to load_percpu_segment(),
    which tells compiler to not instrument this function. However this
    will result in build failure with CONFIG_KASAN=y and CONFIG_OPTIMIZE_INLINING=y.

 b) Add -fno-stack-protector for mm/kasan/kasan.c

Signed-off-by: Andrey Ryabinin <a.ryabinin@...sung.com>
---
 arch/x86/kernel/cpu/common.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4b4f78c..ee5c286 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -389,8 +389,10 @@ void load_percpu_segment(int cpu)
 #ifdef CONFIG_X86_32
 	loadsegment(fs, __KERNEL_PERCPU);
 #else
+	void *gs_base = per_cpu(irq_stack_union.gs_base, cpu);
+
 	loadsegment(gs, 0);
-	wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
+	wrmsrl(MSR_GS_BASE, (unsigned long)gs_base);
 #endif
 	load_stack_canary_segment();
 }
-- 
2.1.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/