Commit 1ce53e2c authored by Alejandro Colomar's avatar Alejandro Colomar Committed by Thomas Gleixner
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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: default avatarAlejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201128123945.4592-1-alx.manpages@gmail.com
parent 997acaf6

include/linux/syscalls.h

+4 −4
Original line number Diff line number Diff line
@@ -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);

kernel/futex.c

+3 −3
Original line number Diff line number Diff line
@@ -3790,8 +3790,8 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, 




SYSCALL_DEFINE6(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)

{

	struct timespec64 ts;

	ktime_t t, *tp = NULL;
@@ -3986,7 +3986,7 @@ COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid, 


#ifdef CONFIG_COMPAT_32BIT_TIME

SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,

		struct old_timespec32 __user *, utime, u32 __user *, uaddr2,

		const struct old_timespec32 __user *, utime, u32 __user *, uaddr2,

		u32, val3)

{

	struct timespec64 ts;