[PATCH stable v4.14 04/32] powerpc: Use barrier_nospec in copy_from_user()

[Michael Ellerman]

commit ddf35cf3764b5a182b178105f57515b42e2634f8 upstream.

Based on the x86 commit doing the same.

See commit 304ec1b05031 ("x86/uaccess: Use __uaccess_begin_nospec()
and uaccess_try_nospec") and b3bbfb3fb5d2 ("x86: Introduce
__uaccess_begin_nospec() and uaccess_try_nospec") for more detail.

In all cases we are ordering the load from the potentially
user-controlled pointer vs a previous branch based on an access_ok()
check or similar.

Base on a patch from Michal Suchanek.

Signed-off-by: Michal Suchanek <msuchanek at suse.de>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
---
 arch/powerpc/include/asm/uaccess.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index cf26e62b268d..bd6d0fb5be9f 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -238,6 +238,7 @@ do {								\
 	__chk_user_ptr(ptr);					\
 	if (!is_kernel_addr((unsigned long)__gu_addr))		\
 		might_fault();					\
+	barrier_nospec();					\
 	__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
 	(x) = (__typeof__(*(ptr)))__gu_val;			\
 	__gu_err;						\
@@ -249,8 +250,10 @@ do {								\
 	__long_type(*(ptr)) __gu_val = 0;				\
 	const __typeof__(*(ptr)) __user *__gu_addr = (ptr);		\
 	might_fault();							\
-	if (access_ok(VERIFY_READ, __gu_addr, (size)))			\
+	if (access_ok(VERIFY_READ, __gu_addr, (size))) {		\
+		barrier_nospec();					\
 		__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
+	}								\
 	(x) = (__force __typeof__(*(ptr)))__gu_val;				\
 	__gu_err;							\
 })
@@ -261,6 +264,7 @@ do {								\
 	__long_type(*(ptr)) __gu_val;				\
 	const __typeof__(*(ptr)) __user *__gu_addr = (ptr);	\
 	__chk_user_ptr(ptr);					\
+	barrier_nospec();					\
 	__get_user_size(__gu_val, __gu_addr, (size), __gu_err);	\
 	(x) = (__force __typeof__(*(ptr)))__gu_val;			\
 	__gu_err;						\
@@ -288,15 +292,19 @@ static inline unsigned long raw_copy_from_user(void *to,
 
 		switch (n) {
 		case 1:
+			barrier_nospec();
 			__get_user_size(*(u8 *)to, from, 1, ret);
 			break;
 		case 2:
+			barrier_nospec();
 			__get_user_size(*(u16 *)to, from, 2, ret);
 			break;
 		case 4:
+			barrier_nospec();
 			__get_user_size(*(u32 *)to, from, 4, ret);
 			break;
 		case 8:
+			barrier_nospec();
 			__get_user_size(*(u64 *)to, from, 8, ret);
 			break;
 		}
@@ -304,6 +312,7 @@ static inline unsigned long raw_copy_from_user(void *to,
 			return 0;
 	}
 
+	barrier_nospec();
 	return __copy_tofrom_user((__force void __user *)to, from, n);
 }
 
-- 
2.20.1