Commit af4e9ef3 authored by David Laight's avatar David Laight Committed by Linus Torvalds
Browse files

uaccess: Fix scoped_user_read_access() for 'pointer to const' 



If a 'const struct foo __user *ptr' is used for the address passed to
scoped_user_read_access() then you get a warning/error

  uaccess.h:691:1: error: initialization discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]

for the

  void __user *_tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl)

assignment.

Fix by using 'auto' for both _tmpptr and the redeclaration of uptr.
Replace the CLASS() with explicit __cleanup() functions on uptr.

Fixes: e497310b ("uaccess: Provide scoped user access regions")
Signed-off-by: default avatarDavid Laight <david.laight.linux@gmail.com>
Reviewed-and-tested-by: default avatarChristophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1b37ac21

include/linux/uaccess.h

+20 −34
Original line number Diff line number Diff line
@@ -647,36 +647,22 @@ static inline void user_access_restore(unsigned long flags) { } 
/* Define RW variant so the below _mode macro expansion works */

#define masked_user_rw_access_begin(u)	masked_user_access_begin(u)

#define user_rw_access_begin(u, s)	user_access_begin(u, s)

#define user_rw_access_end()		user_access_end()



/* Scoped user access */

#define USER_ACCESS_GUARD(_mode)				\

static __always_inline void __user *				\

class_user_##_mode##_begin(void __user *ptr)			\

{								\

	return ptr;						\

}								\

								\

static __always_inline void					\

class_user_##_mode##_end(void __user *ptr)			\

{								\

	user_##_mode##_access_end();				\

}								\

								\

DEFINE_CLASS(user_ ##_mode## _access, void __user *,		\

	     class_user_##_mode##_end(_T),			\

	     class_user_##_mode##_begin(ptr), void __user *ptr)	\

								\

static __always_inline class_user_##_mode##_access_t		\

class_user_##_mode##_access_ptr(void __user *scope)		\

{								\

	return scope;						\

}



USER_ACCESS_GUARD(read)

USER_ACCESS_GUARD(write)

USER_ACCESS_GUARD(rw)

#undef USER_ACCESS_GUARD

/* Cleanup wrapper functions */

static __always_inline void __scoped_user_read_access_end(const void *p)

{

	user_read_access_end();

};

static __always_inline void __scoped_user_write_access_end(const void *p)

{

	user_write_access_end();

};

static __always_inline void __scoped_user_rw_access_end(const void *p)

{

	user_access_end();

};



/**

 * __scoped_user_access_begin - Start a scoped user access
@@ -752,11 +738,11 @@ USER_ACCESS_GUARD(rw) 
 */

#define __scoped_user_access(mode, uptr, size, elbl)				\

for (bool done = false; !done; done = true)					\

	for (void __user *_tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl); \

	for (auto _tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl);	\

	     !done; done = true)						\

		for (CLASS(user_##mode##_access, scope)(_tmpptr); !done; done = true)	\

		/* Force modified pointer usage within the scope */		\

			for (const typeof(uptr) uptr = _tmpptr; !done; done = true)

		for (const auto uptr  __cleanup(__scoped_user_##mode##_access_end) = \

		     _tmpptr; !done; done = true)



/**

 * scoped_user_read_access_size - Start a scoped user read access with given size