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

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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
This commit is contained in:
Alejandro Colomar 2020-11-28 13:39:46 +01:00 committed by Thomas Gleixner
parent 997acaf6b4
commit 1ce53e2c2a
2 changed files with 7 additions and 7 deletions
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8
include/linux/syscalls.h
View File

@ -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);

6
kernel/futex.c
View File

@ -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 @@ err_unlock:
#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;