path: root/kernel/pid_namespace.c
diff options
authorCyrill Gorcunov <gorcunov@openvz.org>2012-10-19 13:56:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-10-19 14:07:47 -0700
commitbbc2e3ef87851bc5430b2b4cf4ca3a2f29baeda6 (patch)
treed9cef396c8370184f23e99480725aa8fde4bea08 /kernel/pid_namespace.c
parentdc36d7e7cd422d69b15e7ec7cc1f021f581a6b6d (diff)
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: Cyrill 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/pid_namespace.c')
1 files changed, 14 insertions, 7 deletions
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 478bad2745e..eb00be20581 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -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;
- 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;
+ }
void zap_pid_ns_processes(struct pid_namespace *pid_ns)