perf: Fix sys_perf_event_open() race against self

stable inclusion
from stable-v5.10.118
commit 3ee8e109c3c316073a3e0f83ec0769c7ee8a7375
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I593PQ
CVE: CVE-2022-1729

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3ee8e109c3c316073a3e0f83ec0769c7ee8a7375

--------------------------------

commit 3ac6487e upstream.

Norbert reported that it's possible to race sys_perf_event_open() such
that the looser ends up in another context from the group leader,
triggering many WARNs.

The move_group case checks for races against itself, but the
!move_group case doesn't, seemingly relying on the previous
group_leader->ctx == ctx check. However, that check is racy due to not
holding any locks at that time.

Therefore, re-check the result after acquiring locks and bailing
if they no longer match.

Additionally, clarify the not_move_group case from the
move_group-vs-move_group race.

Fixes: f63a8daa ("perf: Fix event->ctx locking")
Reported-by: NNorbert Slusarek <nslusarek@gmx.net>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLi Huafei <lihuafei1@huawei.com>
Reviewed-by: NYang Jihong <yangjihong1@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

kernel/events/core.c

@@ -11897,6 +11897,9 @@ SYSCALL_DEFINE5(perf_event_open,
 		 * Do not allow to attach to a group in a different task
 		 * or CPU context. If we're moving SW events, we'll fix
 		 * this up later, so allow that.
+		 *
+		 * Racy, not holding group_leader->ctx->mutex, see comment with
+		 * perf_event_ctx_lock().
 		 */
 		if (!move_group && group_leader->ctx != ctx)
 			goto err_context;
@@ -11964,6 +11967,7 @@ SYSCALL_DEFINE5(perf_event_open,
 			} else {
 				perf_event_ctx_unlock(group_leader, gctx);
 				move_group = 0;
+				goto not_move_group;
 			}
 		}
 
@@ -11980,7 +11984,17 @@ SYSCALL_DEFINE5(perf_event_open,
 		}
 	} else {
 		mutex_lock(&ctx->mutex);
+
+		/*
+		 * Now that we hold ctx->lock, (re)validate group_leader->ctx == ctx,
+		 * see the group_leader && !move_group test earlier.
+		 */
+		if (group_leader && group_leader->ctx != ctx) {
+			err = -EINVAL;
+			goto err_locked;
+		}
 	}
+not_move_group:
 
 	if (ctx->task == TASK_TOMBSTONE) {
 		err = -ESRCH;