* [PATCH RFC] x86/elf: Fix incorrect STACK_RND_MASK for x86_64
@ 2021-10-14 13:27 sxwjean
2021-10-14 16:10 ` Kees Cook
0 siblings, 1 reply; 3+ messages in thread
From: sxwjean @ 2021-10-14 13:27 UTC (permalink / raw)
To: x86
Cc: Xiongwei Song, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
H. Peter Anvin, Gabriel Krisman Bertazi, Andy Lutomirski,
Kees Cook, Chang S. Bae, Al Viro, linux-kernel
From: Xiongwei Song <sxwjean@gmail.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@qemux86-64:~# 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@qemux86-64:~# 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@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Gabriel Krisman Bertazi <krisman@collabora.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: "Chang S. Bae" <chang.seok.bae@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Xiongwei Song <sxwjean@gmail.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
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH RFC] x86/elf: Fix incorrect STACK_RND_MASK for x86_64
2021-10-14 13:27 [PATCH RFC] x86/elf: Fix incorrect STACK_RND_MASK for x86_64 sxwjean
@ 2021-10-14 16:10 ` Kees Cook
2021-10-15 2:21 ` Xiongwei Song
0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2021-10-14 16:10 UTC (permalink / raw)
To: sxwjean
Cc: x86, Xiongwei Song, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
H. Peter Anvin, Gabriel Krisman Bertazi, Andy Lutomirski,
Chang S. Bae, Al Viro, linux-kernel
On Thu, Oct 14, 2021 at 09:27:36PM +0800, sxwjean@me.com wrote:
> From: Xiongwei Song <sxwjean@gmail.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.
Why do we want to _reduce_ entropy here? Perhaps adjust the comment
instead?
-Kees
>
> Before this patch(bit0 ~ bit33 randomized):
> root@qemux86-64:~# 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@qemux86-64:~# 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@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Gabriel Krisman Bertazi <krisman@collabora.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: "Chang S. Bae" <chang.seok.bae@intel.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Xiongwei Song <sxwjean@gmail.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
>
--
Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH RFC] x86/elf: Fix incorrect STACK_RND_MASK for x86_64
2021-10-14 16:10 ` Kees Cook
@ 2021-10-15 2:21 ` Xiongwei Song
0 siblings, 0 replies; 3+ messages in thread
From: Xiongwei Song @ 2021-10-15 2:21 UTC (permalink / raw)
To: Kees Cook
Cc: Xiongwei Song, x86, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
H. Peter Anvin, Gabriel Krisman Bertazi, Andy Lutomirski,
Chang S. Bae, Al Viro, Linux Kernel Mailing List
On Fri, Oct 15, 2021 at 12:10 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Thu, Oct 14, 2021 at 09:27:36PM +0800, sxwjean@me.com wrote:
> > From: Xiongwei Song <sxwjean@gmail.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.
>
> Why do we want to _reduce_ entropy here? Perhaps adjust the comment
> instead?
Hi Kees,
Shouldn't x86_64 have consistent behavior like arm64, riscv or powerpc
on this? I'm not sure if 34 bits is too wasteful for stack. If 34 bits have no
side effects, then I have no objection with your suggestion.
Regards,
Xiongwei
>
> -Kees
>
> >
> > Before this patch(bit0 ~ bit33 randomized):
> > root@qemux86-64:~# 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@qemux86-64:~# 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@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Gabriel Krisman Bertazi <krisman@collabora.com>
> > Cc: Andy Lutomirski <luto@kernel.org>
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: "Chang S. Bae" <chang.seok.bae@intel.com>
> > Cc: Al Viro <viro@zeniv.linux.org.uk>
> > Cc: linux-kernel@vger.kernel.org
> > Signed-off-by: Xiongwei Song <sxwjean@gmail.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
> >
>
> --
> Kees Cook
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-10-14 13:27 [PATCH RFC] x86/elf: Fix incorrect STACK_RND_MASK for x86_64 sxwjean
2021-10-14 16:10 ` Kees Cook
2021-10-15 2:21 ` Xiongwei Song
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