Merge tag 'msm-fixes-2019_08_01' of https://gitlab.freedesktop.org/drm/msm into drm...

[sfrench/cifs-2.6.git] / kernel / cred.c

diff --git a/kernel/cred.c b/kernel/cred.c
index f9a0ce66c9c3e125393f011be7d55a322785ed2e..c0a4c12d38b20ed80254c76acb28c6d060b1df86 100644 (file)
--- 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);