ACK: [Trusty SRU][PATCH 1/1] fix minor infoleak in get_user_ex()

Stefan Bader stefan.bader at canonical.com
Tue Sep 5 13:03:23 UTC 2017


On 05.09.2017 10:43, Kleber Sacilotto de Souza wrote:
> From: Al Viro <viro at ZenIV.linux.org.uk>
> 
> CVE-2016-9178
> 
> get_user_ex(x, ptr) should zero x on failure.  It's not a lot of a leak
> (at most we are leaking uninitialized 64bit value off the kernel stack,
> and in a fairly constrained situation, at that), but the fix is trivial,
> so...
> 
> Cc: stable at vger.kernel.org
> Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
> [ This sat in different branch from the uaccess fixes since mid-August ]
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> (cherry picked from commit 1c109fabbd51863475cd12ac206bdd249aee35af)
> Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---
>  arch/x86/include/asm/uaccess.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 8ec57c07b125..20e5bacf961c 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -383,7 +383,11 @@ do {									\
>  #define __get_user_asm_ex(x, addr, itype, rtype, ltype)			\
>  	asm volatile("1:	mov"itype" %1,%"rtype"0\n"		\
>  		     "2:\n"						\
> -		     _ASM_EXTABLE_EX(1b, 2b)				\
> +		     ".section .fixup,\"ax\"\n"				\
> +                     "3:xor"itype" %"rtype"0,%"rtype"0\n"		\
> +		     "  jmp 2b\n"					\
> +		     ".previous\n"					\
> +		     _ASM_EXTABLE_EX(1b, 3b)				\
>  		     : ltype(x) : "m" (__m(addr)))
>  
>  #define __put_user_nocheck(x, ptr, size)			\
> 


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