[PATCH bpf-next] bpf: Fix NULL dereference in bpf_task_storage

[Martin KaFai Lau <kafai@xxxxxx>]

In bpf_pid_task_storage_update_elem(), it missed to
test the !task_storage_ptr(task) which then could trigger a NULL
pointer exception in bpf_local_storage_update().

Fixes: 4cf1bc1f1045 ("bpf: Implement task local storage")
Tested-by: Roman Gushchin <guro@xxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxxxx>
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
 kernel/bpf/bpf_task_storage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index 39a45fba4fb0..4ef1959a78f2 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -150,7 +150,7 @@ static int bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key,
 	 */
 	WARN_ON_ONCE(!rcu_read_lock_held());
 	task = pid_task(pid, PIDTYPE_PID);
-	if (!task) {
+	if (!task || !task_storage_ptr(task)) {
 		err = -ENOENT;
 		goto out;
 	}
-- 
2.24.1