Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit bbc2e3ef authored by Cyrill Gorcunov's avatar Cyrill Gorcunov Committed by Linus Torvalds
Browse files

pidns: remove recursion from free_pid_ns() 



free_pid_ns() operates in a recursive fashion:

free_pid_ns(parent)
  put_pid_ns(parent)
    kref_put(&ns->kref, free_pid_ns);
      free_pid_ns

thus if there was a huge nesting of namespaces the userspace may trigger
avalanche calling of free_pid_ns leading to kernel stack exhausting and a
panic eventually.

This patch turns the recursion into an iterative loop.

Based on a patch by Andrew Vagin.

[akpm@linux-foundation.org: export put_pid_ns() to modules]
Signed-off-by: default avatarCyrill Gorcunov <gorcunov@openvz.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dc36d7e7

include/linux/pid_namespace.h

+1 −7
Original line number Diff line number Diff line
@@ -47,15 +47,9 @@ static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns) 
}



extern struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *ns);

extern void free_pid_ns(struct kref *kref);

extern void zap_pid_ns_processes(struct pid_namespace *pid_ns);

extern int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd);



static inline void put_pid_ns(struct pid_namespace *ns)

{

	if (ns != &init_pid_ns)

		kref_put(&ns->kref, free_pid_ns);

}

extern void put_pid_ns(struct pid_namespace *ns);



#else /* !CONFIG_PID_NS */

#include <linux/err.h>

kernel/pid_namespace.c

+14 −7
Original line number Diff line number Diff line
@@ -133,19 +133,26 @@ struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old 
	return create_pid_namespace(old_ns);

}



void free_pid_ns(struct kref *kref)

static void free_pid_ns(struct kref *kref)

{

	struct pid_namespace *ns, *parent;

	struct pid_namespace *ns;



	ns = container_of(kref, struct pid_namespace, kref);



	parent = ns->parent;

	destroy_pid_namespace(ns);

}



	if (parent != NULL)

		put_pid_ns(parent);

void put_pid_ns(struct pid_namespace *ns)

{

	struct pid_namespace *parent;



	while (ns != &init_pid_ns) {

		parent = ns->parent;

		if (!kref_put(&ns->kref, free_pid_ns))

			break;

		ns = parent;

	}

}

EXPORT_SYMBOL_GPL(free_pid_ns);

EXPORT_SYMBOL_GPL(put_pid_ns);



void zap_pid_ns_processes(struct pid_namespace *pid_ns)

{