linux-kernel - [PATCH 1/2] fork: allow CLONE

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Date:   Wed,  8 Mar 2023 11:51:26 +0100
From:   Tobias Klauser <tklauser@...tanz.ch>
To:     Christian Brauner <brauner@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrei Vagin <avagin@...il.com>,
        Dmitry Safonov <dima@...sta.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, Andrey Vagin <avagin@...nvz.org>,
        stable@...r.kernel.org
Subject: [PATCH 1/2] fork: allow CLONE_NEWTIME in clone3 flags

Currently, calling clone3() with CLONE_NEWTIME in clone_args->flags
fails with -EINVAL. This is because CLONE_NEWTIME intersects with
CSIGNAL. However, CSIGNAL was deprecated when clone3 was introduced in
commit 7f192e3cd316 ("fork: add clone3"), allowing re-use of that part
of clone flags.

Fix this by explicitly allowing CLONE_NEWTIME in clone3_args_valid. This
is also in line with the respective check in check_unshare_flags which
allow CLONE_NEWTIME for unshare().

Fixes: 769071ac9f20 ("ns: Introduce Time Namespace")
Cc: Andrey Vagin <avagin@...nvz.org>
Cc: Christian Brauner <brauner@...nel.org>
Cc: stable@...r.kernel.org
Signed-off-by: Tobias Klauser <tklauser@...tanz.ch>
---
 kernel/fork.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index f68954d05e89..d8cda4c6de6c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2936,7 +2936,7 @@ static bool clone3_args_valid(struct kernel_clone_args *kargs)
 	 * - make the CLONE_DETACHED bit reusable for clone3
 	 * - make the CSIGNAL bits reusable for clone3
 	 */
-	if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
+	if (kargs->flags & (CLONE_DETACHED | (CSIGNAL & (~CLONE_NEWTIME))))
 		return false;
 
 	if ((kargs->flags & (CLONE_SIGHAND | CLONE_CLEAR_SIGHAND)) ==
-- 
2.39.1