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

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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: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Julien Thierry 2018-09-11 10:14:50 +01:00 committed by Russell King
parent e3aa624343
commit afaf6838f4
3 changed files with 38 additions and 5 deletions
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11
arch/arm/include/asm/assembler.h
View File

@ -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
/*

26
arch/arm/include/asm/uaccess.h
View File

@ -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

6
arch/arm/lib/copy_from_user.S
View File

@ -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"