[PATCH 2/3] seccomp: rework define for SECCOMP_USER_NOTIF_FLAG_CONTINUE

[Manoj Iyer]

From: Christian Brauner <christian.brauner at ubuntu.com>

Switch from BIT(0) to (1UL << 0).
First, there are already two different forms used in the header, so there's
no need to add a third. Second, the BIT() macros is kernel internal and
afaict not actually exposed to userspace. Maybe there's some magic there
I'm missing but it definitely causes issues when compiling a program that
tries to use SECCOMP_USER_NOTIF_FLAG_CONTINUE. It currently fails in the
following way:

	# github.com/lxc/lxd/lxd
	/usr/bin/ld: $WORK/b001/_x003.o: in function
	`__do_user_notification_continue':
	lxd/main_checkfeature.go:240: undefined reference to `BIT'
	collect2: error: ld returned 1 exit status

Switching to (1UL << 0) should prevent that and is more in line what is
already done in the rest of the header.

BugLink: https://bugs.launchpad.net/bugs/1849281

Cc: Kees Cook <keescook at chromium.org>
Cc: Andy Lutomirski <luto at amacapital.net>
Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
Link: https://lore.kernel.org/r/20191024212539.4059-1-christian.brauner@ubuntu.com
Signed-off-by: Kees Cook <keescook at chromium.org>
(cherry picked from commit 23b2c96fad21886c53f5e1a4ffedd45ddd2e85ba
 git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git)
Signed-off-by: Manoj Iyer <manoj.iyer at canonical.com>
---
 include/uapi/linux/seccomp.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
index e48e2fa2d248..be84d87f1f46 100644
--- a/include/uapi/linux/seccomp.h
+++ b/include/uapi/linux/seccomp.h
@@ -103,7 +103,7 @@ struct seccomp_notif {
  * SECCOMP_USER_NOTIF_FLAG_CONTINUE. Note that SECCOMP_RET_TRACE can equally
  * be overriden by SECCOMP_USER_NOTIF_FLAG_CONTINUE.
  */
-#define SECCOMP_USER_NOTIF_FLAG_CONTINUE BIT(0)
+#define SECCOMP_USER_NOTIF_FLAG_CONTINUE (1UL << 0)
 
 struct seccomp_notif_resp {
 	__u64 id;
-- 
2.20.1