fix refcounting of nsproxy object when unshared

When a namespace is unshared, a refcount on the previous nsproxy is
abusively taken, leading to a memory leak of nsproxy objects.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 8 deletions

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 1bc4b55241..9e83b589f7 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -145,13 +145,11 @@ void free_nsproxy(struct nsproxy *ns)
 
 /*
  * Called from unshare. Unshare all the namespaces part of nsproxy.
- * On sucess, returns the new nsproxy and a reference to old nsproxy
- * to make sure it stays around.
+ * On success, returns the new nsproxy.
  */
 int unshare_nsproxy_namespaces(unsigned long unshare_flags,
                 struct nsproxy **new_nsp, struct fs_struct *new_fs)
 {
-        struct nsproxy *old_ns = current->nsproxy;
         int err = 0;
 
         if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
@@ -170,13 +168,9 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
         if (!capable(CAP_SYS_ADMIN))
                 return -EPERM;
 
-        get_nsproxy(old_ns);
-
         *new_nsp = create_new_namespaces(unshare_flags, current,
                                 new_fs ? new_fs : current->fs);
-        if (IS_ERR(*new_nsp)) {
+        if (IS_ERR(*new_nsp))
                 err = PTR_ERR(*new_nsp);
-                put_nsproxy(old_ns);
-        }
         return err;
 }