Revert "perf: Paper over the hw.target problems"

euler inclusion
category: bugfix
bugzilla: 9513/11006
CVE: NA
--------------------------------------------------

This reverts commit b772baf9a14ab4975e8884a399a4e0bab2fb6bf9.

we merge the patch b772baf9a14a ("perf: Paper over the
hw.target problems") to reslove an use-after-free issue
(bugzilla #9513/#11006).  but it cause some new problem
(bugzilla #11050/#11049) in this version.

So just revert it.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/events/core.c

@@ -2104,27 +2104,6 @@ static void perf_remove_from_context(struct perf_event *event, unsigned long fla
 
 	event_function_call(event, __perf_remove_from_context, (void *)flags);
 
-	/*
-	 * This is as passable as any hw.target handling out there;
-	 * hw.target implies task context, therefore, no migration.
-	 * Which means that we can only get here at the teardown.
-	 */
-	if (event->hw.target) {
-		/*
-		 * Now, the problem with, say uprobes, is that they
-		 * use hw.target for context in their ->destroy()
-		 * callbacks. Supposedly, they may need to poke at
-		 * its contents, so better call it while we still
-		 * have the task.
-		 */
-		if (event->destroy) {
-			event->destroy(event);
-			event->destroy = NULL;
-		}
-		put_task_struct(event->hw.target);
-		event->hw.target = NULL;
-	}
-
 	/*
 	 * The above event_function_call() can NO-OP when it hits
 	 * TASK_TOMBSTONE. In that case we must already have been detached