Commit 5cd62333 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc: Implement user_access_begin and friends 



Today, when a function like strncpy_from_user() is called,
the userspace access protection is de-activated and re-activated
for every word read.

By implementing user_access_begin and friends, the protection
is de-activated at the beginning of the copy and re-activated at the
end.

Implement user_access_begin(), user_access_end() and
unsafe_get_user(), unsafe_put_user() and unsafe_copy_to_user()

For the time being, we keep user_access_save() and
user_access_restore() as nops.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/36d4fbf9e56a75994aca4ee2214c77b26a5a8d35.1579866752.git.christophe.leroy@c-s.fr
parent bedb4dbe

arch/powerpc/include/asm/uaccess.h

+66 −19
Original line number Diff line number Diff line
@@ -91,9 +91,14 @@ static inline int __access_ok(unsigned long addr, unsigned long size, 
	__put_user_check((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))



#define __get_user(x, ptr) \

	__get_user_nocheck((x), (ptr), sizeof(*(ptr)))

	__get_user_nocheck((x), (ptr), sizeof(*(ptr)), true)

#define __put_user(x, ptr) \

	__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))

	__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), true)



#define __get_user_allowed(x, ptr) \

	__get_user_nocheck((x), (ptr), sizeof(*(ptr)), false)

#define __put_user_allowed(x, ptr) \

	__put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), false)



#define __get_user_inatomic(x, ptr) \

	__get_user_nosleep((x), (ptr), sizeof(*(ptr)))
@@ -138,10 +143,9 @@ extern long __put_user_bad(void); 
		: "r" (x), "b" (addr), "i" (-EFAULT), "0" (err))

#endif /* __powerpc64__ */



#define __put_user_size(x, ptr, size, retval)			\

#define __put_user_size_allowed(x, ptr, size, retval)		\

do {								\

	retval = 0;						\

	allow_write_to_user(ptr, size);				\

	switch (size) {						\

	  case 1: __put_user_asm(x, ptr, retval, "stb"); break;	\

	  case 2: __put_user_asm(x, ptr, retval, "sth"); break;	\
@@ -149,17 +153,26 @@ do { \ 
	  case 8: __put_user_asm2(x, ptr, retval); break;	\

	  default: __put_user_bad();				\

	}							\

} while (0)



#define __put_user_size(x, ptr, size, retval)			\

do {								\

	allow_write_to_user(ptr, size);				\

	__put_user_size_allowed(x, ptr, size, retval);		\

	prevent_write_to_user(ptr, size);			\

} while (0)



#define __put_user_nocheck(x, ptr, size)			\

#define __put_user_nocheck(x, ptr, size, do_allow)			\

({								\

	long __pu_err;						\

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

	if (!is_kernel_addr((unsigned long)__pu_addr))		\

		might_fault();					\

	__chk_user_ptr(ptr);					\

	if (do_allow)								\

		__put_user_size((x), __pu_addr, (size), __pu_err);		\

	else									\

		__put_user_size_allowed((x), __pu_addr, (size), __pu_err);	\

	__pu_err;						\

})
@@ -236,13 +249,12 @@ extern long __get_user_bad(void); 
		: "b" (addr), "i" (-EFAULT), "0" (err))

#endif /* __powerpc64__ */



#define __get_user_size(x, ptr, size, retval)			\

#define __get_user_size_allowed(x, ptr, size, retval)		\

do {								\

	retval = 0;						\

	__chk_user_ptr(ptr);					\

	if (size > sizeof(x))					\

		(x) = __get_user_bad();				\

	allow_read_from_user(ptr, size);			\

	switch (size) {						\

	case 1: __get_user_asm(x, ptr, retval, "lbz"); break;	\

	case 2: __get_user_asm(x, ptr, retval, "lhz"); break;	\
@@ -250,6 +262,12 @@ do { \ 
	case 8: __get_user_asm2(x, ptr, retval);  break;	\

	default: (x) = __get_user_bad();			\

	}							\

} while (0)



#define __get_user_size(x, ptr, size, retval)			\

do {								\

	allow_read_from_user(ptr, size);			\

	__get_user_size_allowed(x, ptr, size, retval);		\

	prevent_read_from_user(ptr, size);			\

} while (0)
@@ -260,7 +278,7 @@ do { \ 
#define __long_type(x) \

	__typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))



#define __get_user_nocheck(x, ptr, size)			\

#define __get_user_nocheck(x, ptr, size, do_allow)			\

({								\

	long __gu_err;						\

	__long_type(*(ptr)) __gu_val;				\
@@ -269,7 +287,10 @@ do { \ 
	if (!is_kernel_addr((unsigned long)__gu_addr))		\

		might_fault();					\

	barrier_nospec();					\

	if (do_allow)								\

		__get_user_size(__gu_val, __gu_addr, (size), __gu_err);		\

	else									\

		__get_user_size_allowed(__gu_val, __gu_addr, (size), __gu_err);	\

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

	__gu_err;						\

})
@@ -356,33 +377,40 @@ static inline unsigned long raw_copy_from_user(void *to, 
	return ret;

}



static inline unsigned long raw_copy_to_user(void __user *to,

		const void *from, unsigned long n)

static inline unsigned long

raw_copy_to_user_allowed(void __user *to, const void *from, unsigned long n)

{

	unsigned long ret;

	if (__builtin_constant_p(n) && (n <= 8)) {

		ret = 1;

		unsigned long ret = 1;



		switch (n) {

		case 1:

			__put_user_size(*(u8 *)from, (u8 __user *)to, 1, ret);

			__put_user_size_allowed(*(u8 *)from, (u8 __user *)to, 1, ret);

			break;

		case 2:

			__put_user_size(*(u16 *)from, (u16 __user *)to, 2, ret);

			__put_user_size_allowed(*(u16 *)from, (u16 __user *)to, 2, ret);

			break;

		case 4:

			__put_user_size(*(u32 *)from, (u32 __user *)to, 4, ret);

			__put_user_size_allowed(*(u32 *)from, (u32 __user *)to, 4, ret);

			break;

		case 8:

			__put_user_size(*(u64 *)from, (u64 __user *)to, 8, ret);

			__put_user_size_allowed(*(u64 *)from, (u64 __user *)to, 8, ret);

			break;

		}

		if (ret == 0)

			return 0;

	}



	return __copy_tofrom_user(to, (__force const void __user *)from, n);

}



static inline unsigned long

raw_copy_to_user(void __user *to, const void *from, unsigned long n)

{

	unsigned long ret;



	allow_write_to_user(to, n);

	ret = __copy_tofrom_user(to, (__force const void __user *)from, n);

	ret = raw_copy_to_user_allowed(to, from, n);

	prevent_write_to_user(to, n);

	return ret;

}
@@ -428,4 +456,23 @@ extern long __copy_from_user_flushcache(void *dst, const void __user *src, 
extern void memcpy_page_flushcache(char *to, struct page *page, size_t offset,

			   size_t len);



static __must_check inline bool user_access_begin(const void __user *ptr, size_t len)

{

	if (unlikely(!access_ok(ptr, len)))

		return false;

	allow_read_write_user((void __user *)ptr, ptr, len);

	return true;

}

#define user_access_begin	user_access_begin

#define user_access_end		prevent_current_access_user



static inline unsigned long user_access_save(void) { return 0UL; }

static inline void user_access_restore(unsigned long flags) { }



#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)

#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)

#define unsafe_put_user(x, p, e) unsafe_op_wrap(__put_user_allowed(x, p), e)

#define unsafe_copy_to_user(d, s, l, e) \

	unsafe_op_wrap(raw_copy_to_user_allowed(d, s, l), e)



#endif	/* _ARCH_POWERPC_UACCESS_H */

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