filldir[64]: remove WARN_ON_ONCE() for bad directory entries

mainline inclusion
from mainline-v5.4-rc4
commit b9959c7a347d6adbb558fba7e36e9fef3cba3b07
category: bugfix
bugzilla: 13690
CVE: CVE-2019-10220

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

This was always meant to be a temporary thing, just for testing and to
see if it actually ever triggered.

The only thing that reported it was syzbot doing disk image fuzzing, and
then that warning is expected.  So let's just remove it before -rc4,
because the extra sanity testing should probably go to -stable, but we
don't want the warning to do so.

Reported-by: syzbot+3031f712c7ad5dd4d926@syzkaller.appspotmail.com
Fixes: 8a23eb804ca4 ("Make filldir[64]() verify the directory entry filename is valid")
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/readdir.c

@@ -105,9 +105,9 @@ EXPORT_SYMBOL(iterate_dir);
  */
 static int verify_dirent_name(const char *name, int len)
 {
-	if (WARN_ON_ONCE(!len))
+	if (!len)
 		return -EIO;
-	if (WARN_ON_ONCE(memchr(name, '/', len)))
+	if (memchr(name, '/', len))
 		return -EIO;
 	return 0;
 }