cifs: do not include page data when checking signature

stable inclusion
from stable-v4.19.271
commit 19f0577dd34b250e1595f8dd577d9c2b6c1dc85d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6DPF8
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v4.19.271&id=19f0577dd34b250e1595f8dd577d9c2b6c1dc85d



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

commit 30b2b219 upstream.

On async reads, page data is allocated before sending.  When the
response is received but it has no data to fill (e.g.
STATUS_END_OF_FILE), __calc_signature() will still include the pages in
its computation, leading to an invalid signature check.

This patch fixes this by not setting the async read smb_rqst page data
(zeroed by default) if its got_bytes is 0.

This can be reproduced/verified with xfstests generic/465.

Cc: <stable@vger.kernel.org>
Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Conflict:
  fs/cifs/smb2pdu.c

Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
Reviewed-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>