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

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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: e497310b4f ("uaccess: Provide scoped user access regions")
Signed-off-by: David Laight <david.laight.linux@gmail.com>
Reviewed-and-tested-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Laight 2026-03-02 13:27:51 +00:00 committed by Linus Torvalds
parent 1b37ac211a
commit af4e9ef3d7
1 changed files with 20 additions and 34 deletions
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54
include/linux/uaccess.h
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@ -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
@ -750,13 +736,13 @@ USER_ACCESS_GUARD(rw)
*
* Don't use directly. Use scoped_masked_user_$MODE_access() instead.
*/
#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); \
!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)
#define __scoped_user_access(mode, uptr, size, elbl) \
for (bool done = false; !done; done = true) \
for (auto _tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl); \
!done; done = true) \
/* Force modified pointer usage within the scope */ \
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