linux-kernel - Re: + core_pattern-set-core-helpers-root-and-namespace-to-crashing-process .patch added to -mm tree

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Date:	Mon, 17 Dec 2012 13:34:28 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Neil Horman <nhorman@...driver.com>,
	Daniel Berrange <berrange@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re:  +
	core_pattern-set-core-helpers-root-and-namespace-to-crashing-process
	.patch added to -mm tree

@@ -455,6 +468,14 @@ static int umh_pipe_setup(struct subproc
 	/* and disallow core files too */
 	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 
+
+	if (cp->switch_ns) {
+		get_fs_root(cp->cprocess->fs, &root);
+		set_fs_root(current->fs, &root);
+		switch_task_namespaces(current, cp->cprocess->nsproxy);

How? You can't simply change ->nsproxy this way.

If nothing else this breaks sys_getpid(), no?

And a lot more problems, afaics. For example, this thread can continue
to run after, say, this cprocess->nsproxy->pid_ns was already destroyed.
zap_pid_ns_processes() obviously won't see this thread.

Even ->nsproxy itself can go away. Just suppose that the coredumping
task is the only process in this namespace (sub-init).

Oleg.

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