linux-kernel - [PATCH] clone3: add a check for the user struct size if CLONE_INTO

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Message-ID: <20200412203123.GA5869@asgard.redhat.com>
Date:   Sun, 12 Apr 2020 22:31:23 +0200
From:   Eugene Syromiatnikov <esyr@...hat.com>
To:     linux-kernel@...r.kernel.org,
        Christian Brauner <christian@...uner.io>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Dmitry V. Levin" <ldv@...linux.org>
Subject: [PATCH] clone3: add a check for the user struct size if
 CLONE_INTO_CGROUP is set

Passing CLONE_INTO_CGROUP with an under-sized structure (that doesn't
properly contain cgroup field) seems like garbage input, especially
considering the fact that fd 0 is a valid descriptor.

Signed-off-by: Eugene Syromiatnikov <esyr@...hat.com>
---
 kernel/fork.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 11bcc7e..8c700f8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2639,7 +2639,8 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
 		     !valid_signal(args.exit_signal)))
 		return -EINVAL;
 
-	if ((args.flags & CLONE_INTO_CGROUP) && args.cgroup > INT_MAX)
+	if ((args.flags & CLONE_INTO_CGROUP) &&
+	    (args.cgroup > INT_MAX || usize < CLONE_ARGS_SIZE_VER2))
 		return -EINVAL;
 
 	*kargs = (struct kernel_clone_args){
-- 
2.1.4