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Date: Thu, 14 Oct 2021 21:27:36 +0800
From: sxwjean@...com
To: x86@...nel.org
Cc: Xiongwei Song <sxwjean@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
Gabriel Krisman Bertazi <krisman@...labora.com>,
Andy Lutomirski <luto@...nel.org>,
Kees Cook <keescook@...omium.org>,
"Chang S. Bae" <chang.seok.bae@...el.com>,
Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: [PATCH RFC] x86/elf: Fix incorrect STACK_RND_MASK for x86_64
From: Xiongwei Song <sxwjean@...il.com>
According to the comment for stack randomization of x86, the range of
randomization is 1GB, which occupies 30 valid bits in binary. And in
x86_64, PAGE_SHIFT occupies 12 bits, then the STACK_RND_MASK should
occupy 18 bits for 1GB.
The current range of randomization is :
0x3fffff << PAGE_SHIFT
, which occupies 34 bits.
This patch changed 0x3fffff to 0x3ffff, which makes the range of stack
randomization is real 1GB.
Before this patch(bit0 ~ bit33 randomized):
root@...ux86-64:~# for i in {1..20};do cat /proc/self/maps | grep stack;done
7ffddf971000-7ffddf992000 rw-p 00000000 00:00 0 [stack]
7ffc4e0d4000-7ffc4e0f5000 rw-p 00000000 00:00 0 [stack]
7fff5898e000-7fff589af000 rw-p 00000000 00:00 0 [stack]
7ffcf910b000-7ffcf912c000 rw-p 00000000 00:00 0 [stack]
7ffce829d000-7ffce82be000 rw-p 00000000 00:00 0 [stack]
7ffec72d9000-7ffec72fa000 rw-p 00000000 00:00 0 [stack]
7ffd6e256000-7ffd6e277000 rw-p 00000000 00:00 0 [stack]
7ffe14120000-7ffe14141000 rw-p 00000000 00:00 0 [stack]
7ffe21549000-7ffe2156a000 rw-p 00000000 00:00 0 [stack]
7ffdc9d33000-7ffdc9d54000 rw-p 00000000 00:00 0 [stack]
7ffe1ced4000-7ffe1cef5000 rw-p 00000000 00:00 0 [stack]
7ffcb0440000-7ffcb0461000 rw-p 00000000 00:00 0 [stack]
7ffc84515000-7ffc84536000 rw-p 00000000 00:00 0 [stack]
7ffe557dd000-7ffe557fe000 rw-p 00000000 00:00 0 [stack]
7ffdcb7e4000-7ffdcb805000 rw-p 00000000 00:00 0 [stack]
7ffc6f989000-7ffc6f9aa000 rw-p 00000000 00:00 0 [stack]
7ffd9322a000-7ffd9324b000 rw-p 00000000 00:00 0 [stack]
7ffea8e34000-7ffea8e55000 rw-p 00000000 00:00 0 [stack]
7ffc594ff000-7ffc59520000 rw-p 00000000 00:00 0 [stack]
7ffe8db65000-7ffe8db86000 rw-p 00000000 00:00 0 [stack]
After this patch(bit0 ~ bit29 randomized):
root@...ux86-64:~# for i in {1..20};do cat /proc/self/maps | grep stack;done
7fffd0ed2000-7fffd0ef3000 rw-p 00000000 00:00 0 [stack]
7fffdf555000-7fffdf576000 rw-p 00000000 00:00 0 [stack]
7ffffec0e000-7ffffec2f000 rw-p 00000000 00:00 0 [stack]
7fffcfa0f000-7fffcfa30000 rw-p 00000000 00:00 0 [stack]
7fffff75d000-7fffff77e000 rw-p 00000000 00:00 0 [stack]
7fffd1d11000-7fffd1d32000 rw-p 00000000 00:00 0 [stack]
7fffc7850000-7fffc7871000 rw-p 00000000 00:00 0 [stack]
7fffc956e000-7fffc958f000 rw-p 00000000 00:00 0 [stack]
7fffdf7be000-7fffdf7df000 rw-p 00000000 00:00 0 [stack]
7fffeffdf000-7ffff0000000 rw-p 00000000 00:00 0 [stack]
7fffd7d7f000-7fffd7da0000 rw-p 00000000 00:00 0 [stack]
7fffe3d23000-7fffe3d44000 rw-p 00000000 00:00 0 [stack]
7fffde4b7000-7fffde4d8000 rw-p 00000000 00:00 0 [stack]
7fffd477a000-7fffd479b000 rw-p 00000000 00:00 0 [stack]
7fffc0e95000-7fffc0eb6000 rw-p 00000000 00:00 0 [stack]
7fffdbdda000-7fffdbdfb000 rw-p 00000000 00:00 0 [stack]
7fffec737000-7fffec758000 rw-p 00000000 00:00 0 [stack]
7fffed163000-7fffed184000 rw-p 00000000 00:00 0 [stack]
7ffff9a9c000-7ffff9abd000 rw-p 00000000 00:00 0 [stack]
7fffff945000-7fffff966000 rw-p 00000000 00:00 0 [stack]
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Gabriel Krisman Bertazi <krisman@...labora.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Kees Cook <keescook@...omium.org>
Cc: "Chang S. Bae" <chang.seok.bae@...el.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Xiongwei Song <sxwjean@...il.com>
---
arch/x86/include/asm/elf.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 29fea180a665..0b7a5510ebd5 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -343,7 +343,7 @@ extern unsigned long get_sigframe_size(void);
#else /* CONFIG_X86_32 */
/* 1GB for 64bit, 8MB for 32bit */
-#define __STACK_RND_MASK(is32bit) ((is32bit) ? 0x7ff : 0x3fffff)
+#define __STACK_RND_MASK(is32bit) ((is32bit) ? 0x7ff : 0x3ffff)
#define STACK_RND_MASK __STACK_RND_MASK(mmap_is_ia32())
#define ARCH_DLINFO \
--
2.30.2
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