ext4: verify dir block before splitting it

stable inclusion
from stable-v5.10.121
commit da2f05919238c7bdc6e28c79539f55c8355408bb
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=da2f05919238c7bdc6e28c79539f55c8355408bb



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

commit 46c116b9 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: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>