The patch titled
Subject: pidns: remove recursion from free_pid_ns()
has been removed from the -mm tree. Its filename was
pidns-remove-recursion-from-free_pid_ns-v5.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxx: export put_pid_ns() to modules]
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Andrew Vagin <avagin@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pid_namespace.h | 8 +-------
kernel/pid_namespace.c | 21 ++++++++++++++-------
2 files changed, 15 insertions(+), 14 deletions(-)
diff -puN include/linux/pid_namespace.h~pidns-remove-recursion-from-free_pid_ns-v5 include/linux/pid_namespace.h
--- a/include/linux/pid_namespace.h~pidns-remove-recursion-from-free_pid_ns-v5
+++ a/include/linux/pid_namespace.h
@@ -47,15 +47,9 @@ static inline struct pid_namespace *get_
}
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 -puN kernel/pid_namespace.c~pidns-remove-recursion-from-free_pid_ns-v5 kernel/pid_namespace.c
--- a/kernel/pid_namespace.c~pidns-remove-recursion-from-free_pid_ns-v5
+++ a/kernel/pid_namespace.c
@@ -133,19 +133,26 @@ struct pid_namespace *copy_pid_ns(unsign
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);
+}
+
+void put_pid_ns(struct pid_namespace *ns)
+{
+ struct pid_namespace *parent;
- if (parent != NULL)
- put_pid_ns(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)
{
_
Patches currently in -mm which might be from gorcunov@xxxxxxxxxx are
linux-next.patch
proc-check-vma-vm_file-before-dereferencing.patch
tools-testing-selftests-kcmp-kcmp_testc-print-reason-for-failure-in-kcmp_test.patch
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