netdev - Re: [PATCH 11/18] maccess: remove strncpy_from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wiivWJ70PotzCK-j7K4Y612NJBA2d+iN6Rz-bfMxCpwjQ@mail.gmail.com>
Date:   Wed, 13 May 2020 16:03:20 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Christoph Hellwig <hch@....de>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-parisc@...r.kernel.org,
        linux-um <linux-um@...ts.infradead.org>,
        Netdev <netdev@...r.kernel.org>, bpf@...r.kernel.org,
        Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 11/18] maccess: remove strncpy_from_unsafe

On Wed, May 13, 2020 at 3:36 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> It's used for both.

Daniel, BPF real;ly needs to make up its mind about that.

You *cannot* use ti for both.

Yes, it happens to work on x86 and some other architectures.

But on other architectures, the exact same pointer value can be a
kernel pointer or a user pointer.

> Given this is enabled on pretty much all program types, my
> assumption would be that usage is still more often on kernel memory than user one.

You need to pick one.

If you know it is a user pointer, use strncpy_from_user() (possibly
with disable_pagefault() aka strncpy_from_user_nofault()).

And if you know it is a kernel pointer, use strncpy_from_unsafe() (aka
strncpy_from_kernel_nofault()).

You really can't pick the "randomly one or the other guess what I mean " option.

                  Linus