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arm64: Factor out PAN enabling/disabling into separate uaccess_* macros 

This patch moves the directly coded alternatives for turning PAN on/off
into separate uaccess_{enable,disable} macros or functions. The asm
macros take a few arguments which will be used in subsequent patches.

Note that any (unlikely) access that the compiler might generate between
uaccess_enable() and uaccess_disable(), other than those explicitly
specified by the user access code, will not be protected by PAN.

Cc: Will Deacon <will.deacon@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Catalin Marinas 2016-07-01 14:58:21 +01:00
parent a8ada146f5
commit bd38967d40
7 changed files with 93 additions and 58 deletions
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17
arch/arm64/include/asm/futex.h
View File

@ -21,15 +21,12 @@
#include <linux/futex.h>
#include <linux/uaccess.h>
#include <asm/alternative.h>
#include <asm/cpufeature.h>
#include <asm/errno.h>
#include <asm/sysreg.h>
#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg) \
do { \
uaccess_enable(); \
asm volatile( \
ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN) \
" prfm pstl1strm, %2\n" \
"1: ldxr %w1, %2\n" \
insn "\n" \
@ -44,11 +41,11 @@
" .popsection\n" \
_ASM_EXTABLE(1b, 4b) \
_ASM_EXTABLE(2b, 4b) \
ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN) \
: "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp) \
: "r" (oparg), "Ir" (-EFAULT) \
: "memory")
: "memory"); \
uaccess_disable(); \
} while (0)
static inline int
futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
@ -118,8 +115,8 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
return -EFAULT;
uaccess_enable();
asm volatile("// futex_atomic_cmpxchg_inatomic\n"
ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
" prfm pstl1strm, %2\n"
"1: ldxr %w1, %2\n"
" sub %w3, %w1, %w4\n"
@ -134,10 +131,10 @@ ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
" .popsection\n"
_ASM_EXTABLE(1b, 4b)
_ASM_EXTABLE(2b, 4b)
ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
: "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp)
: "r" (oldval), "r" (newval), "Ir" (-EFAULT)
: "memory");
uaccess_disable();
*uval = val;
return ret;

79
arch/arm64/include/asm/uaccess.h
View File

@ -18,6 +18,11 @@
#ifndef __ASM_UACCESS_H
#define __ASM_UACCESS_H
#include <asm/alternative.h>
#include <asm/sysreg.h>
#ifndef __ASSEMBLY__
/*
* User space memory access functions
*/
@ -26,10 +31,8 @@
#include <linux/string.h>
#include <linux/thread_info.h>
#include <asm/alternative.h>
#include <asm/cpufeature.h>
#include <asm/ptrace.h>
#include <asm/sysreg.h>
#include <asm/errno.h>
#include <asm/memory.h>
#include <asm/compiler.h>
@ -119,6 +122,44 @@ static inline void set_fs(mm_segment_t fs)
" .long (" #from " - .), (" #to " - .)\n" \
" .popsection\n"
/*
* User access enabling/disabling.
*/
#define __uaccess_disable(alt) \
do { \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), alt, \
CONFIG_ARM64_PAN)); \
} while (0)
#define __uaccess_enable(alt) \
do { \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), alt, \
CONFIG_ARM64_PAN)); \
} while (0)
static inline void uaccess_disable(void)
{
__uaccess_disable(ARM64_HAS_PAN);
}
static inline void uaccess_enable(void)
{
__uaccess_enable(ARM64_HAS_PAN);
}
/*
* These functions are no-ops when UAO is present.
*/
static inline void uaccess_disable_not_uao(void)
{
__uaccess_disable(ARM64_ALT_PAN_NOT_UAO);
}
static inline void uaccess_enable_not_uao(void)
{
__uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
}
/*
* The "__xxx" versions of the user access functions do not verify the address
* space - it must have been done previously with a separate "access_ok()"
@ -146,8 +187,7 @@ static inline void set_fs(mm_segment_t fs)
do { \
unsigned long __gu_val; \
__chk_user_ptr(ptr); \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
CONFIG_ARM64_PAN)); \
uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
__get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
@ -168,9 +208,8 @@ do { \
default: \
BUILD_BUG(); \
} \
uaccess_disable_not_uao(); \
(x) = (__force __typeof__(*(ptr)))__gu_val; \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
CONFIG_ARM64_PAN)); \
} while (0)
#define __get_user(x, ptr) \
@ -215,8 +254,7 @@ do { \
do { \
__typeof__(*(ptr)) __pu_val = (x); \
__chk_user_ptr(ptr); \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_ALT_PAN_NOT_UAO,\
CONFIG_ARM64_PAN)); \
uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
__put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
@ -237,8 +275,7 @@ do { \
default: \
BUILD_BUG(); \
} \
asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_ALT_PAN_NOT_UAO,\
CONFIG_ARM64_PAN)); \
uaccess_disable_not_uao(); \
} while (0)
#define __put_user(x, ptr) \
@ -331,4 +368,26 @@ extern long strncpy_from_user(char *dest, const char __user *src, long count);
extern __must_check long strlen_user(const char __user *str);
extern __must_check long strnlen_user(const char __user *str, long n);
#else /* __ASSEMBLY__ */
#include <asm/assembler.h>
/*
* User access enabling/disabling macros. These are no-ops when UAO is
* present.
*/
.macro uaccess_disable_not_uao, tmp1
alternative_if ARM64_ALT_PAN_NOT_UAO
SET_PSTATE_PAN(1)
alternative_else_nop_endif
.endm
.macro uaccess_enable_not_uao, tmp1, tmp2
alternative_if ARM64_ALT_PAN_NOT_UAO
SET_PSTATE_PAN(0)
alternative_else_nop_endif
.endm
#endif /* __ASSEMBLY__ */
#endif /* __ASM_UACCESS_H */

11
arch/arm64/kernel/armv8_deprecated.c
View File

@ -14,7 +14,6 @@
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <asm/alternative.h>
#include <asm/cpufeature.h>
#include <asm/insn.h>
#include <asm/opcodes.h>
@ -285,10 +284,10 @@ static void __init register_insn_emulation_sysctl(struct ctl_table *table)
#define __SWP_LL_SC_LOOPS 4
#define __user_swpX_asm(data, addr, res, temp, temp2, B) \
do { \
uaccess_enable(); \
__asm__ __volatile__( \
" mov %w3, %w7\n" \
ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN) \
"0: ldxr"B" %w2, [%4]\n" \
"1: stxr"B" %w0, %w1, [%4]\n" \
" cbz %w0, 2f\n" \
@ -306,12 +305,12 @@ static void __init register_insn_emulation_sysctl(struct ctl_table *table)
" .popsection" \
_ASM_EXTABLE(0b, 4b) \
_ASM_EXTABLE(1b, 4b) \
ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \
CONFIG_ARM64_PAN) \
: "=&r" (res), "+r" (data), "=&r" (temp), "=&r" (temp2) \
: "r" (addr), "i" (-EAGAIN), "i" (-EFAULT), \
"i" (__SWP_LL_SC_LOOPS) \
: "memory")
: "memory"); \
uaccess_disable(); \
} while (0)
#define __user_swp_asm(data, addr, res, temp, temp2) \
__user_swpX_asm(data, addr, res, temp, temp2, "")

11
arch/arm64/lib/clear_user.S
View File

@ -17,10 +17,7 @@
*/
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
#include <asm/uaccess.h>
.text
@ -33,8 +30,7 @@
* Alignment fixed up by hardware.
*/
ENTRY(__clear_user)
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_enable_not_uao x2, x3
mov x2, x1 // save the size for fixup return
subs x1, x1, #8
b.mi 2f
@ -54,8 +50,7 @@ uao_user_alternative 9f, strh, sttrh, wzr, x0, 2
b.mi 5f
uao_user_alternative 9f, strb, sttrb, wzr, x0, 0
5: mov x0, #0
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_disable_not_uao x2
ret
ENDPROC(__clear_user)

11
arch/arm64/lib/copy_from_user.S
View File

@ -16,11 +16,8 @@
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/cache.h>
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
#include <asm/uaccess.h>
/*
* Copy from user space to a kernel buffer (alignment handled by the hardware)
@ -67,12 +64,10 @@
end .req x5
ENTRY(__arch_copy_from_user)
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_enable_not_uao x3, x4
add end, x0, x2
#include "copy_template.S"
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_disable_not_uao x3
mov x0, #0 // Nothing to copy
ret
ENDPROC(__arch_copy_from_user)

11
arch/arm64/lib/copy_in_user.S
View File

@ -18,11 +18,8 @@
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/cache.h>
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
#include <asm/uaccess.h>
/*
* Copy from user space to user space (alignment handled by the hardware)
@ -68,12 +65,10 @@
end .req x5
ENTRY(__copy_in_user)
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_enable_not_uao x3, x4
add end, x0, x2
#include "copy_template.S"
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_disable_not_uao x3
mov x0, #0
ret
ENDPROC(__copy_in_user)

11
arch/arm64/lib/copy_to_user.S
View File

@ -16,11 +16,8 @@
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/cache.h>
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
#include <asm/uaccess.h>
/*
* Copy to user space from a kernel buffer (alignment handled by the hardware)
@ -66,12 +63,10 @@
end .req x5
ENTRY(__arch_copy_to_user)
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_enable_not_uao x3, x4
add end, x0, x2
#include "copy_template.S"
ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_ALT_PAN_NOT_UAO, \
CONFIG_ARM64_PAN)
uaccess_disable_not_uao x3
mov x0, #0
ret
ENDPROC(__arch_copy_to_user)