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Date: Tue, 13 Sep 2016 18:46:31 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Will Deacon <will.deacon@....com>,
James Morse <james.morse@....com>,
Kees Cook <keescook@...omium.org>,
Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
AKASHI Takahiro <takahiro.akashi@...aro.org>,
kernel-hardening@...ts.openwall.com
Subject: [PATCH v3 1/7] 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@....com>
Cc: James Morse <james.morse@....com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Mark Rutland <mark.rutland@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
---
arch/arm64/include/asm/futex.h | 14 +++----
arch/arm64/include/asm/uaccess.h | 79 ++++++++++++++++++++++++++++++++----
arch/arm64/kernel/armv8_deprecated.c | 10 ++---
arch/arm64/lib/clear_user.S | 8 ++--
arch/arm64/lib/copy_from_user.S | 8 ++--
arch/arm64/lib/copy_in_user.S | 8 ++--
arch/arm64/lib/copy_to_user.S | 8 ++--
7 files changed, 95 insertions(+), 40 deletions(-)
diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
index f2585cdd32c2..71dfa3b42313 100644
--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h
@@ -27,9 +27,9 @@
#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 +44,11 @@
" .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 +118,8 @@ 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 +134,10 @@ 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;
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index c47257c91b77..cc6c32d4dcc4 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -18,6 +18,8 @@
#ifndef __ASM_UACCESS_H
#define __ASM_UACCESS_H
+#ifndef __ASSEMBLY__
+
/*
* User space memory access functions
*/
@@ -112,6 +114,44 @@ static inline void set_fs(mm_segment_t fs)
" .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()"
* call.
@@ -138,8 +178,7 @@ 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), \
@@ -160,9 +199,8 @@ 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) \
@@ -207,8 +245,7 @@ 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), \
@@ -229,8 +266,7 @@ 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) \
@@ -321,4 +357,31 @@ 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/alternative.h>
+#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_not ARM64_ALT_PAN_NOT_UAO
+ nop
+alternative_else
+ SET_PSTATE_PAN(1)
+alternative_endif
+ .endm
+
+ .macro uaccess_enable_not_uao, tmp1, tmp2
+alternative_if_not ARM64_ALT_PAN_NOT_UAO
+ nop
+alternative_else
+ SET_PSTATE_PAN(0)
+alternative_endif
+ .endm
+
+#endif /* __ASSEMBLY__ */
+
#endif /* __ASM_UACCESS_H */
diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index 42ffdb54e162..7156e7bfcd89 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -281,9 +281,9 @@ static void __init register_insn_emulation_sysctl(struct ctl_table *table)
* Error-checking SWP macros implemented using ldxr{b}/stxr{b}
*/
#define __user_swpX_asm(data, addr, res, temp, B) \
+do { \
+ uaccess_enable(); \
__asm__ __volatile__( \
- ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \
- CONFIG_ARM64_PAN) \
"0: ldxr"B" %w2, [%3]\n" \
"1: stxr"B" %w0, %w1, [%3]\n" \
" cbz %w0, 2f\n" \
@@ -299,11 +299,11 @@ 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" (addr), "i" (-EAGAIN), "i" (-EFAULT) \
- : "memory")
+ : "memory"); \
+ uaccess_disable(); \
+} while (0)
#define __user_swp_asm(data, addr, res, temp) \
__user_swpX_asm(data, addr, res, temp, "")
diff --git a/arch/arm64/lib/clear_user.S b/arch/arm64/lib/clear_user.S
index 5d1cad3ce6d6..08b5f18ba604 100644
--- a/arch/arm64/lib/clear_user.S
+++ b/arch/arm64/lib/clear_user.S
@@ -17,10 +17,10 @@
*/
#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 +33,7 @@
* 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 +53,7 @@ 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)
diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
index 0b90497d4424..6505ec81f1da 100644
--- a/arch/arm64/lib/copy_from_user.S
+++ b/arch/arm64/lib/copy_from_user.S
@@ -16,11 +16,11 @@
#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 +67,10 @@
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)
diff --git a/arch/arm64/lib/copy_in_user.S b/arch/arm64/lib/copy_in_user.S
index f7292dd08c84..9b04ff3ab610 100644
--- a/arch/arm64/lib/copy_in_user.S
+++ b/arch/arm64/lib/copy_in_user.S
@@ -18,11 +18,11 @@
#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 +68,10 @@
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)
diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S
index 7a7efe255034..8077e4f34d56 100644
--- a/arch/arm64/lib/copy_to_user.S
+++ b/arch/arm64/lib/copy_to_user.S
@@ -16,11 +16,11 @@
#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 +66,10 @@
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)
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