futex: Change utime parameter to be 'const ... *'

futex(2) says that 'utime' is a pointer to 'const'.  The implementation
doesn't use 'const'; however, it _never_ modifies the contents of utime.

- futex() either uses 'utime' as a pointer to struct or as a 'u32'.

- In case it's used as a 'u32', it makes a copy of it, and of course it is
  not dereferenced.

- In case it's used as a 'struct __kernel_timespec __user *', the pointer
  is not dereferenced inside the futex() definition, and it is only passed
  to a function: get_timespec64(), which accepts a 'const struct
  __kernel_timespec __user *'.

[ tglx: Make the same change to the compat syscall and fixup the prototypes. ]

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201128123945.4592-1-alx.manpages@gmail.com

1 files changed, 4 insertions, 4 deletions

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index f3929aff39cf..5cb74edd9a4f 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -583,11 +583,11 @@ asmlinkage long sys_unshare(unsigned long unshare_flags);
 
 /* kernel/futex.c */
 asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
-			struct __kernel_timespec __user *utime, u32 __user *uaddr2,
-			u32 val3);
+			  const struct __kernel_timespec __user *utime,
+			  u32 __user *uaddr2, u32 val3);
 asmlinkage long sys_futex_time32(u32 __user *uaddr, int op, u32 val,
-			struct old_timespec32 __user *utime, u32 __user *uaddr2,
-			u32 val3);
+				 const struct old_timespec32 __user *utime,
+				 u32 __user *uaddr2, u32 val3);
 asmlinkage long sys_get_robust_list(int pid,
 				    struct robust_list_head __user * __user *head_ptr,
 				    size_t __user *len_ptr);