[PATCH v3 2/4] arm64: uaccess: Implement unsafe accessors

Julien Thierry
2019-01-15T13:58:48Z

Current implementation of get/put_user_unsafe default to get/put_user
which toggle PAN before each access, despite having been told by the caller
that multiple accesses to user memory were about to happen.

Provide implementations for user_access_begin/end to turn PAN off/on and
implement unsafe accessors that assume PAN was already turned off.

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>

---
arch/arm64/include/asm/uaccess.h | 79 ++++++++++++++++++++++++++++++----------
1 file changed, 59 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 8e40808..6a70c75 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -270,31 +270,26 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)

#define __raw_get_user(x, ptr, err) \
do { \
- unsigned long __gu_val; \
- __chk_user_ptr(ptr); \
- uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
- __get_user_asm("ldrb", "ldtrb", "%w", __gu_val, (ptr), \
+ __get_user_asm("ldrb", "ldtrb", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 2: \
- __get_user_asm("ldrh", "ldtrh", "%w", __gu_val, (ptr), \
+ __get_user_asm("ldrh", "ldtrh", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 4: \
- __get_user_asm("ldr", "ldtr", "%w", __gu_val, (ptr), \
+ __get_user_asm("ldr", "ldtr", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 8: \
- __get_user_asm("ldr", "ldtr", "%x", __gu_val, (ptr), \
+ __get_user_asm("ldr", "ldtr", "%x", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
default: \
BUILD_BUG(); \
} \
- uaccess_disable_not_uao(); \
- (x) = (__force __typeof__(*(ptr)))__gu_val; \
} while (0)

#define __get_user_error(x, ptr, err) \
@@ -302,8 +297,13 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
__typeof__(*(ptr)) __user *__p = (ptr); \
might_fault(); \
if (access_ok(__p, sizeof(*__p))) { \
+ unsigned long __gu_val; \
+ __chk_user_ptr(__p); \
__p = uaccess_mask_ptr(__p); \
- __raw_get_user((x), __p, (err)); \
+ uaccess_enable_not_uao(); \
+ __raw_get_user(__gu_val, __p, (err)); \
+ uaccess_disable_not_uao(); \
+ (x) = (__force __typeof__(*__p)) __gu_val; \
} else { \
(x) = 0; (err) = -EFAULT; \
} \
@@ -334,30 +334,26 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)

#define __raw_put_user(x, ptr, err) \
do { \
- __typeof__(*(ptr)) __pu_val = (x); \
- __chk_user_ptr(ptr); \
- uaccess_enable_not_uao(); \
switch (sizeof(*(ptr))) { \
case 1: \
- __put_user_asm("strb", "sttrb", "%w", __pu_val, (ptr), \
+ __put_user_asm("strb", "sttrb", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 2: \
- __put_user_asm("strh", "sttrh", "%w", __pu_val, (ptr), \
+ __put_user_asm("strh", "sttrh", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 4: \
- __put_user_asm("str", "sttr", "%w", __pu_val, (ptr), \
+ __put_user_asm("str", "sttr", "%w", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
case 8: \
- __put_user_asm("str", "sttr", "%x", __pu_val, (ptr), \
+ __put_user_asm("str", "sttr", "%x", (x), (ptr), \
(err), ARM64_HAS_UAO); \
break; \
default: \
BUILD_BUG(); \
} \
- uaccess_disable_not_uao(); \
} while (0)

#define __put_user_error(x, ptr, err) \
@@ -365,9 +361,13 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
__typeof__(*(ptr)) __user *__p = (ptr); \
might_fault(); \
if (access_ok(__p, sizeof(*__p))) { \
+ __typeof__(*(ptr)) __pu_val = (x); \
+ __chk_user_ptr(__p); \
__p = uaccess_mask_ptr(__p); \
- __raw_put_user((x), __p, (err)); \
- } else { \
+ uaccess_enable_not_uao(); \
+ __raw_put_user(__pu_val, __p, (err)); \
+ uaccess_disable_not_uao(); \
+ } else { \
(err) = -EFAULT; \
} \
} while (0)
@@ -381,6 +381,45 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)

#define put_user __put_user

+static __must_check inline bool user_access_begin(const void __user *ptr,
+ size_t len)
+{
+ if (unlikely(!access_ok(ptr, len)))
+ return false;
+
+ uaccess_enable_not_uao();
+ return true;
+}
+#define user_access_begin(ptr, len) user_access_begin(ptr, len)
+#define user_access_end() uaccess_disable_not_uao()
+
+#define unsafe_get_user(x, ptr, err) \
+do { \
+ __typeof__(*(ptr)) __user *__p = (ptr); \
+ unsigned long __gu_val; \
+ int __gu_err = 0; \
+ might_fault(); \
+ __chk_user_ptr(__p); \
+ __p = uaccess_mask_ptr(__p); \
+ __raw_get_user(__gu_val, __p, __gu_err); \
+ (x) = (__force __typeof__(*__p)) __gu_val; \
+ if (__gu_err != 0) \
+ goto err; \
+} while (0)
+
+#define unsafe_put_user(x, ptr, err) \
+do { \
+ __typeof__(*(ptr)) __user *__p = (ptr); \
+ __typeof__(*(ptr)) __pu_val = (x); \
+ int __pu_err = 0; \
+ might_fault(); \
+ __chk_user_ptr(__p); \
+ __p = uaccess_mask_ptr(__p); \
+ __raw_put_user(__pu_val, __p, __pu_err); \
+ if (__pu_err != 0) \
+ goto err; \
+} while (0)
+
extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
#define raw_copy_from_user(to, from, n) \
({ \
--
1.9.1