On Mon, Jul 31, 2023 at 07:42:11PM +0200, Thomas Gleixner wrote:
> Aargh. This is really nasty to make FUTEX2_64 0x3 and abuse it to test
> the flags for validity. Intuitive and obvious is something else.
Like so then?
--- a/include/uapi/linux/futex.h
+++ b/include/uapi/linux/futex.h
@@ -57,6 +57,8 @@
/* 0x40 */
#define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG
+#define FUTEX2_SIZE_MASK 0x03
+
/* do not use */
#define FUTEX_32 FUTEX2_32 /* historical accident :-( */
--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -183,7 +183,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad
return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
}
-#define FUTEX2_MASK (FUTEX2_64 | FUTEX2_PRIVATE)
+#define FUTEX2_MASK (FUTEX2_SIZE_MASK | FUTEX2_PRIVATE)
/**
* futex_parse_waitv - Parse a waitv array from userspace
@@ -208,11 +208,11 @@ static int futex_parse_waitv(struct fute
return -EINVAL;
if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
- if ((aux.flags & FUTEX2_64) == FUTEX2_64)
+ if ((aux.flags & FUTEX2_SIZE_MASK) == FUTEX2_64)
return -EINVAL;
}
- if ((aux.flags & FUTEX2_64) != FUTEX2_32)
+ if ((aux.flags & FUTEX2_SIZE_MASK) != FUTEX2_32)
return -EINVAL;
futexv[i].w.flags = aux.flags;
