Commit 3b82a6ea authored by James Morse's avatar James Morse Committed by Catalin Marinas
Browse files

Revert "arm64: uaccess: implement unsafe accessors" 



This reverts commit a1f33941.

The unsafe accessors allow the PAN enable/disable calls to be made
once for a group of accesses. Adding these means we can now have
sequences that look like this:

| user_access_begin();
| unsafe_put_user(static-value, x, err);
| unsafe_put_user(helper-that-sleeps(), x, err);
| user_access_end();

Calling schedule() without taking an exception doesn't switch the
PSTATE or TTBRs. We can switch out of a uaccess-enabled region, and
run other code with uaccess enabled for a different thread.

We can also switch from uaccess-disabled code back into this region,
meaning the unsafe_put_user()s will fault.

For software-PAN, threads that do this will get stuck as
handle_mm_fault() will determine the page has already been mapped in,
but we fault again as the page tables aren't loaded.

To solve this we need code in __switch_to() that save/restores the
PAN state.

Acked-by: default avatarJulien Thierry <julien.thierry@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 742fafa5

arch/arm64/include/asm/uaccess.h

+15 −46
Original line number Diff line number Diff line
@@ -276,9 +276,11 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr) 
	: "+r" (err), "=&r" (x)						\

	: "r" (addr), "i" (-EFAULT))



#define __get_user_err_unsafe(x, ptr, err)				\

#define __get_user_err(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),  \
@@ -299,24 +301,17 @@ do { \ 
	default:							\

		BUILD_BUG();						\

	}								\

	(x) = (__force __typeof__(*(ptr)))__gu_val;			\

} while (0)



#define __get_user_err_check(x, ptr, err)				\

do {									\

	__chk_user_ptr(ptr);						\

	uaccess_enable_not_uao();					\

	__get_user_err_unsafe((x), (ptr), (err));			\

	uaccess_disable_not_uao();					\

	(x) = (__force __typeof__(*(ptr)))__gu_val;			\

} while (0)



#define __get_user_err(x, ptr, err, accessor)				\

#define __get_user_check(x, ptr, err)					\

({									\

	__typeof__(*(ptr)) __user *__p = (ptr);				\

	might_fault();							\

	if (access_ok(VERIFY_READ, __p, sizeof(*__p))) {		\

		__p = uaccess_mask_ptr(__p);				\

		accessor((x), __p, (err));				\

		__get_user_err((x), __p, (err));			\

	} else {							\

		(x) = 0; (err) = -EFAULT;				\

	}								\
@@ -324,14 +319,14 @@ do { \ 


#define __get_user_error(x, ptr, err)					\

({									\

	__get_user_err((x), (ptr), (err), __get_user_err_check);	\

	__get_user_check((x), (ptr), (err));				\

	(void)0;							\

})



#define __get_user(x, ptr)						\

({									\

	int __gu_err = 0;						\

	__get_user_err((x), (ptr), __gu_err, __get_user_err_check);	\

	__get_user_check((x), (ptr), __gu_err);				\

	__gu_err;							\

})
@@ -351,9 +346,11 @@ do { \ 
	: "+r" (err)							\

	: "r" (x), "r" (addr), "i" (-EFAULT))



#define __put_user_err_unsafe(x, ptr, err)				\

#define __put_user_err(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),	\
@@ -374,24 +371,16 @@ do { \ 
	default:							\

		BUILD_BUG();						\

	}								\

} while (0)





#define __put_user_err_check(x, ptr, err)				\

do {									\

	__chk_user_ptr(ptr);						\

	uaccess_enable_not_uao();					\

	__put_user_err_unsafe((x), (ptr), (err));			\

	uaccess_disable_not_uao();					\

} while (0)



#define __put_user_err(x, ptr, err, accessor)				\

#define __put_user_check(x, ptr, err)					\

({									\

	__typeof__(*(ptr)) __user *__p = (ptr);				\

	might_fault();							\

	if (access_ok(VERIFY_WRITE, __p, sizeof(*__p))) {		\

		__p = uaccess_mask_ptr(__p);				\

		accessor((x), __p, (err));				\

		__put_user_err((x), __p, (err));			\

	} else	{							\

		(err) = -EFAULT;					\

	}								\
@@ -399,39 +388,19 @@ do { \ 


#define __put_user_error(x, ptr, err)					\

({									\

	__put_user_err((x), (ptr), (err), __put_user_err_check);	\

	__put_user_check((x), (ptr), (err));				\

	(void)0;							\

})



#define __put_user(x, ptr)						\

({									\

	int __pu_err = 0;						\

	__put_user_err((x), (ptr), __pu_err, __put_user_err_check);	\

	__put_user_check((x), (ptr), __pu_err);				\

	__pu_err;							\

})



#define put_user	__put_user





#define user_access_begin()	uaccess_enable_not_uao()

#define user_access_end()	uaccess_disable_not_uao()



#define unsafe_get_user(x, ptr, err)					\

do {									\

	int __gu_err = 0;						\

	__get_user_err((x), (ptr), __gu_err, __get_user_err_unsafe);	\

	if (__gu_err != 0)						\

		goto err;						\

} while (0)



#define unsafe_put_user(x, ptr, err)					\

do {									\

	int __pu_err = 0;						\

	__put_user_err((x), (ptr), __pu_err, __put_user_err_unsafe);	\

	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)					\

({									\

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