Fix recursive lock in free_uid()/free_user_ns()

free_uid() and free_user_ns() are corecursive when CONFIG_USER_SCHED=n,
but free_user_ns() is called from free_uid() by way of uid_hash_remove(),
which requires uidhash_lock to be held.  free_user_ns() then calls
free_uid() to complete the destruction.

Fix this by deferring the destruction of the user_namespace.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 315bcd375224..cc4f45361dbb 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -13,6 +13,7 @@ struct user_namespace {
         struct kref             kref;
         struct hlist_head       uidhash_table[UIDHASH_SZ];
         struct user_struct      *creator;
+        struct work_struct      destroyer;
 };
 
 extern struct user_namespace init_user_ns;