do_epoll_ctl(): clean the failure exits up a bit

stable inclusion
from linux-4.19.142
commit dcb6e6efb3298e59d90ee05c6ed33de810314892
CVE: CVE-2020-0466

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

commit 52c47969 upstream.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/eventpoll.c

@@ -2096,10 +2096,8 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
 			mutex_lock(&epmutex);
 			if (is_file_epoll(tf.file)) {
 				error = -ELOOP;
-				if (ep_loop_check(ep, tf.file) != 0) {
-					clear_tfile_check_list();
+				if (ep_loop_check(ep, tf.file) != 0)
 					goto error_tgt_fput;
-				}
 			} else {
 				get_file(tf.file);
 				list_add(&tf.file->f_tfile_llink,
@@ -2128,8 +2126,6 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
 			error = ep_insert(ep, &epds, tf.file, fd, full_check);
 		} else
 			error = -EEXIST;
-		if (full_check)
-			clear_tfile_check_list();
 		break;
 	case EPOLL_CTL_DEL:
 		if (epi)
@@ -2152,8 +2148,10 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
 	mutex_unlock(&ep->mtx);
 
 error_tgt_fput:
-	if (full_check)
+	if (full_check) {
+		clear_tfile_check_list();
 		mutex_unlock(&epmutex);
+	}
 
 	fdput(tf);
 error_fput: