diff options
| author | Cyrill Gorcunov <gorcunov@openvz.org> | 2012-10-19 13:56:53 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-10-19 14:07:47 -0700 |
| commit | bbc2e3ef87851bc5430b2b4cf4ca3a2f29baeda6 (patch) | |
| tree | d9cef396c8370184f23e99480725aa8fde4bea08 | |
| parent | dc36d7e7cd422d69b15e7ec7cc1f021f581a6b6d (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>
| -rw-r--r-- | include/linux/pid_namespace.h | 8 | ||||
| -rw-r--r-- | kernel/pid_namespace.c | 21 |
2 files changed, 15 insertions, 14 deletions
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h index 00474b04714..65e3e87eacc 100644 --- a/include/linux/pid_namespace.h +++ b/include/linux/pid_namespace.h @@ -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> 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; 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) { |