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Commit afaf6838 authored by Julien Thierry's avatar Julien Thierry Committed by Russell King
Browse files

ARM: 8796/1: spectre-v1,v1.1: provide helpers for address sanitization 



Introduce C and asm helpers to sanitize user address, taking the
address range they target into account.

Use asm helper for existing sanitization in __copy_from_user().

Signed-off-by: default avatarJulien Thierry <julien.thierry@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@armlinux.org.uk>
parent e3aa6243

arch/arm/include/asm/assembler.h

+11 −0
Original line number Diff line number Diff line
@@ -467,6 +467,17 @@ THUMB( orr \reg , \reg , #PSR_T_BIT ) 
#endif

	.endm



	.macro uaccess_mask_range_ptr, addr:req, size:req, limit:req, tmp:req

#ifdef CONFIG_CPU_SPECTRE

	sub	\tmp, \limit, #1

	subs	\tmp, \tmp, \addr	@ tmp = limit - 1 - addr

	addhs	\tmp, \tmp, #1		@ if (tmp >= 0) {

	subhss	\tmp, \tmp, \size	@ tmp = limit - (addr + size) }

	movlo	\addr, #0		@ if (tmp < 0) addr = NULL

	csdb

#endif

	.endm



	.macro	uaccess_disable, tmp, isb=1

#ifdef CONFIG_CPU_SW_DOMAIN_PAN

	/*

arch/arm/include/asm/uaccess.h

+26 −0
Original line number Diff line number Diff line
@@ -99,6 +99,32 @@ static inline void set_fs(mm_segment_t fs) 
#define __inttype(x) \

	__typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))



/*

 * Sanitise a uaccess pointer such that it becomes NULL if addr+size

 * is above the current addr_limit.

 */

#define uaccess_mask_range_ptr(ptr, size)			\

	((__typeof__(ptr))__uaccess_mask_range_ptr(ptr, size))

static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr,

						    size_t size)

{

	void __user *safe_ptr = (void __user *)ptr;

	unsigned long tmp;



	asm volatile(

	"	sub	%1, %3, #1\n"

	"	subs	%1, %1, %0\n"

	"	addhs	%1, %1, #1\n"

	"	subhss	%1, %1, %2\n"

	"	movlo	%0, #0\n"

	: "+r" (safe_ptr), "=&r" (tmp)

	: "r" (size), "r" (current_thread_info()->addr_limit)

	: "cc");



	csdb();

	return safe_ptr;

}



/*

 * Single-value transfer routines.  They automatically use the right

 * size if we just have the right pointer type.  Note that the functions

arch/arm/lib/copy_from_user.S

+1 −5
Original line number Diff line number Diff line
@@ -93,11 +93,7 @@ ENTRY(arm_copy_from_user) 
#ifdef CONFIG_CPU_SPECTRE

	get_thread_info r3

	ldr	r3, [r3, #TI_ADDR_LIMIT]

	adds	ip, r1, r2	@ ip=addr+size

	sub	r3, r3, #1	@ addr_limit - 1

	cmpcc	ip, r3		@ if (addr+size > addr_limit - 1)

	movcs	r1, #0		@ addr = NULL

	csdb

	uaccess_mask_range_ptr r1, r2, r3, ip

#endif



#include "copy_template.S"