ext4: verify dir block before splitting it

stable inclusion
from stable-4.19.247
commit 78398c2b2cc14f9a9c8592cf6d334c5a479ed611
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5FNPY


CVE: NA

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

commit 46c116b920ebec58031f0a78c5ea9599b0d2a371 upstream.

Before splitting a directory block verify its directory entries are sane
so that the splitting code does not access memory it should not.

Cc: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220518093332.13986-1-jack@suse.cz


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>