xen/netfront: don't use gnttab_query_foreign_access() for mapped status

stable inclusion
from stable-v5.10.105
commit f6690dd9446a2a4bd9b024f00f71dd827a98317f
bugzilla: 186480 https://gitee.com/src-openeuler/kernel/issues/I50W9L
CVE: CVE-2022-23037

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f6690dd9446a2a4bd9b024f00f71dd827a98317f



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

Commit 31185df7 upstream.

It isn't enough to check whether a grant is still being in use by
calling gnttab_query_foreign_access(), as a mapping could be realized
by the other side just after having called that function.

In case the call was done in preparation of revoking a grant it is
better to do so via gnttab_end_foreign_access_ref() and check the
success of that operation instead.

This is CVE-2022-23037 / part of XSA-396.

Reported-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>