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authorDavid Howells <dhowells@redhat.com>2009-02-27 14:03:03 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-02-27 16:26:21 -0800
commit5170836679185357dc1b7660bad13287b39e1e33 (patch)
tree0b470820e11df7c7eef7e3161657aefe90c7c35e
parent8ca2f156b06bdcbfd1ab543355279246d05e2499 (diff)
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>
-rw-r--r--include/linux/user_namespace.h1
-rw-r--r--kernel/user_namespace.c21
2 files changed, 18 insertions, 4 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;
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 79084311ee57..076c7c8215b0 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -60,12 +60,25 @@ int create_user_ns(struct cred *new)
return 0;
}
-void free_user_ns(struct kref *kref)
+/*
+ * Deferred destructor for a user namespace. This is required because
+ * free_user_ns() may be called with uidhash_lock held, but we need to call
+ * back to free_uid() which will want to take the lock again.
+ */
+static void free_user_ns_work(struct work_struct *work)
{
- struct user_namespace *ns;
-
- ns = container_of(kref, struct user_namespace, kref);
+ struct user_namespace *ns =
+ container_of(work, struct user_namespace, destroyer);
free_uid(ns->creator);
kfree(ns);
}
+
+void free_user_ns(struct kref *kref)
+{
+ struct user_namespace *ns =
+ container_of(kref, struct user_namespace, kref);
+
+ INIT_WORK(&ns->destroyer, free_user_ns_work);
+ schedule_work(&ns->destroyer);
+}
EXPORT_SYMBOL(free_user_ns);