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-rw-r--r--kernel/cred.c21
1 files changed, 19 insertions, 2 deletions
diff --git a/kernel/cred.c b/kernel/cred.c
index f9a0ce66c9c3..c0a4c12d38b2 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -144,7 +144,10 @@ void __put_cred(struct cred *cred)
BUG_ON(cred == current->cred);
BUG_ON(cred == current->real_cred);
- call_rcu(&cred->rcu, put_cred_rcu);
+ if (cred->non_rcu)
+ put_cred_rcu(&cred->rcu);
+ else
+ call_rcu(&cred->rcu, put_cred_rcu);
}
EXPORT_SYMBOL(__put_cred);
@@ -261,6 +264,7 @@ struct cred *prepare_creds(void)
old = task->cred;
memcpy(new, old, sizeof(struct cred));
+ new->non_rcu = 0;
atomic_set(&new->usage, 1);
set_cred_subscribers(new, 0);
get_group_info(new->group_info);
@@ -544,7 +548,19 @@ const struct cred *override_creds(const struct cred *new)
validate_creds(old);
validate_creds(new);
- get_cred(new);
+
+ /*
+ * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
+ *
+ * That means that we do not clear the 'non_rcu' flag, since
+ * we are only installing the cred into the thread-synchronous
+ * '->cred' pointer, not the '->real_cred' pointer that is
+ * visible to other threads under RCU.
+ *
+ * Also note that we did validate_creds() manually, not depending
+ * on the validation in 'get_cred()'.
+ */
+ get_new_cred((struct cred *)new);
alter_cred_subscribers(new, 1);
rcu_assign_pointer(current->cred, new);
alter_cred_subscribers(old, -1);
@@ -681,6 +697,7 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
validate_creds(old);
*new = *old;
+ new->non_rcu = 0;
atomic_set(&new->usage, 1);
set_cred_subscribers(new, 0);
get_uid(new->user);