Comment 2 for bug 1999094

Confirmed that reverting this commit fixes the issue

commit 1c64ee93e442926be20205b5659499cfd405bff0
Author: Al Viro <email address hidden>
Date: Mon Sep 26 11:59:14 2022 -0400

    don't use __kernel_write() on kmap_local_page()

    BugLink: https://bugs.launchpad.net/bugs/1994078

    [ Upstream commit 06bbaa6dc53cb72040db952053432541acb9adc7 ]

    passing kmap_local_page() result to __kernel_write() is unsafe -
    random ->write_iter() might (and 9p one does) get unhappy when
    passed ITER_KVEC with pointer that came from kmap_local_page().

    Fix by providing a variant of __kernel_write() that takes an iov_iter
    from caller (__kernel_write() becomes a trivial wrapper) and adding
    dump_emit_page() that parallels dump_emit(), except that instead of
    __kernel_write() it uses __kernel_write_iter() with ITER_BVEC source.

    Fixes: 3159ed57792b "fs/coredump: use kmap_local_page()"
    Signed-off-by: Al Viro <email address hidden>
    Signed-off-by: Sasha Levin <email address hidden>
    Signed-off-by: Kamal Mostafa <email address hidden>