From bbc2e3ef87851bc5430b2b4cf4ca3a2f29baeda6 Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov Date: Fri, 19 Oct 2012 13:56:53 -0700 Subject: 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 Cc: Andrew Vagin Cc: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Pavel Emelyanov Cc: Greg KH Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/pid_namespace.h | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) (limited to 'include/linux') diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h index 00474b047145..65e3e87eacc5 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 -- cgit v1.2.2