From 8382fcac1b813ad0a4e68a838fc7ae93fa39eda0 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Thu, 20 Dec 2012 19:26:06 -0800 Subject: [PATCH] pidns: Outlaw thread creation after unshare(CLONE_NEWPID) The sequence: unshare(CLONE_NEWPID) clone(CLONE_THREAD|CLONE_SIGHAND|CLONE_VM) Creates a new process in the new pid namespace without setting pid_ns->child_reaper. After forking this results in a NULL pointer dereference. Avoid this and other nonsense scenarios that can show up after creating a new pid namespace with unshare by adding a new check in copy_prodcess. Pointed-out-by: Oleg Nesterov Acked-by: Oleg Nesterov Signed-off-by: "Eric W. Biederman" --- kernel/fork.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/fork.c b/kernel/fork.c index a31b823b3c2d..65ca6d27f24e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1166,6 +1166,14 @@ static struct task_struct *copy_process(unsigned long clone_flags, current->signal->flags & SIGNAL_UNKILLABLE) return ERR_PTR(-EINVAL); + /* + * If the new process will be in a different pid namespace + * don't allow the creation of threads. + */ + if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) && + (task_active_pid_ns(current) != current->nsproxy->pid_ns)) + return ERR_PTR(-EINVAL); + retval = security_task_create(clone_flags); if (retval) goto fork_out;