From 1ce53e2c2ac069e7b3c400a427002a70deb4a916 Mon Sep 17 00:00:00 2001

From: Alejandro Colomar <alx.manpages@gmail.com>

Date: Sat, 28 Nov 2020 13:39:46 +0100

Subject: [PATCH] futex: Change utime parameter to be 'const ... *'

Git-commit: 1ce53e2c2ac069e7b3c400a427002a70deb4a916

Patch-mainline: v5.12-rc1

References: git-fixes

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

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>

---

 include/linux/syscalls.h | 8 ++++----

 kernel/futex.c           | 6 +++---

 2 files changed, 7 insertions(+), 7 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);

diff --git a/kernel/futex.c b/kernel/futex.c

index c47d1015d759..d0775aab8da9 100644

--- a/kernel/futex.c

+++ b/kernel/futex.c

@@ -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;

-- 

2.26.2