[PATCH v3 4/4] x86/uaccess: Fix implicit cast of __user pointer

From: Jann Horn
Date: Fri Mar 29 2019 - 17:47:19 EST


The first two arguments of __user_atomic_cmpxchg_inatomic() are:

- `uval` is a kernel pointer into which the old value should be stored
- `ptr` is the user pointer on which the cmpxchg should operate

This means that casting `uval` to `__typeof__(ptr)` is wrong. Since `uval`
is only used once inside the macro, just get rid of __uval and use `(uval)`
directly.

Reviewed-by: Mukesh Ojha <mojha@xxxxxxxxxxxxxx>
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
---
arch/x86/include/asm/uaccess.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 1954dd5552a2..a21f2a2f17bf 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -585,7 +585,6 @@ extern void __cmpxchg_wrong_size(void)
#define __user_atomic_cmpxchg_inatomic(uval, ptr, old, new, size) \
({ \
int __ret = 0; \
- __typeof__(ptr) __uval = (uval); \
__typeof__(*(ptr)) __old = (old); \
__typeof__(*(ptr)) __new = (new); \
__uaccess_begin_nospec(); \
@@ -661,7 +660,7 @@ extern void __cmpxchg_wrong_size(void)
__cmpxchg_wrong_size(); \
} \
__uaccess_end(); \
- *__uval = __old; \
+ *(uval) = __old; \
__ret; \
})

--
2.21.0.392.gf8f6787159e-goog