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pidns: kill the unnecessary CLONE_NEWPID in copy_process()

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Commit 8382fcac1b81 ("pidns: Outlaw thread creation after
unshare(CLONE_NEWPID)") nacks CLONE_NEWPID if the forking process
unshared pid_ns.  This is correct but unnecessary, copy_pid_ns() does
the same check.

Remove the CLONE_NEWPID check to cleanup the code and prepare for the
next change.

Test-case:

	static int child(void *arg)
	{
		return 0;
	}

	static char stack[16 * 1024];

	int main(void)
	{
		pid_t pid;

		assert(unshare(CLONE_NEWUSER | CLONE_NEWPID) == 0);

		pid = clone(child, stack + sizeof(stack) / 2,
				CLONE_NEWPID | SIGCHLD, NULL);
		assert(pid < 0 && errno == EINVAL);

		return 0;
	}

clone(CLONE_NEWPID) correctly fails with or without this change.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Colin Walters <walters@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2013-09-11 14:19:40 -07:00 committed by Linus Torvalds
parent e79f525e99
commit 5167246a8a
1 changed files with 2 additions and 3 deletions
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5
kernel/fork.c
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@ -1177,9 +1177,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
* allow it to share a thread group or signal handlers with the
* forking task.
*/
if ((clone_flags & (CLONE_SIGHAND | CLONE_NEWPID)) &&
(task_active_pid_ns(current) !=
current->nsproxy->pid_ns_for_children))
if ((clone_flags & CLONE_SIGHAND) && (task_active_pid_ns(current) !=
current->nsproxy->pid_ns_for_children))
return ERR_PTR(-EINVAL);
retval = security_task_create(clone_flags);