userfaultfd: uapi: fix UFFDIO_CONTINUE ioctl request definition

This ioctl request reads from uffdio_continue structure written by
userspace which justifies _IOC_WRITE flag.  It also writes back to that
structure which justifies _IOC_READ flag.

See NOTEs in include/uapi/asm-generic/ioctl.h for more information.

Fixes: f6191471 ("userfaultfd: add UFFDIO_CONTINUE ioctl")
Signed-off-by: NGleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Acked-by: NPeter Xu <peterx@redhat.com>
Reviewed-by: NAxel Rasmussen <axelrasmussen@google.com>
Reviewed-by: NDmitry V. Levin <ldv@altlinux.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/uapi/linux/userfaultfd.h

@@ -80,7 +80,7 @@
 				      struct uffdio_zeropage)
 #define UFFDIO_WRITEPROTECT	_IOWR(UFFDIO, _UFFDIO_WRITEPROTECT, \
 				      struct uffdio_writeprotect)
-#define UFFDIO_CONTINUE		_IOR(UFFDIO, _UFFDIO_CONTINUE,	\
+#define UFFDIO_CONTINUE		_IOWR(UFFDIO, _UFFDIO_CONTINUE,	\
 				      struct uffdio_continue)
 
 /* read() structure */