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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Christoph Hellwig <hch@lst.de>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-parisc@vger.kernel.org,
	linux-um <linux-um@lists.infradead.org>,
	Netdev <netdev@vger.kernel.org>,
	bpf@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 11/18] maccess: remove strncpy_from_unsafe
Date: Wed, 13 May 2020 16:03:20 -0700	[thread overview]
Message-ID: <CAHk-=wiivWJ70PotzCK-j7K4Y612NJBA2d+iN6Rz-bfMxCpwjQ@mail.gmail.com> (raw)
In-Reply-To: <0c1a7066-b269-9695-b94a-bb5f4f20ebd8@iogearbox.net>

On Wed, May 13, 2020 at 3:36 PM Daniel Borkmann <daniel@iogearbox.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

  reply	other threads:[~2020-05-13 23:03 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13 16:00 clean up and streamline probe_kernel_* and friends v2 Christoph Hellwig
2020-05-13 16:00 ` [PATCH 01/18] maccess: unexport probe_kernel_write and probe_user_write Christoph Hellwig
2020-05-13 16:00 ` [PATCH 02/18] maccess: remove various unused weak aliases Christoph Hellwig
2020-05-13 16:00 ` [PATCH 03/18] maccess: remove duplicate kerneldoc comments Christoph Hellwig
2020-05-13 16:00 ` [PATCH 04/18] maccess: clarify " Christoph Hellwig
2020-05-13 16:00 ` [PATCH 05/18] maccess: update the top of file comment Christoph Hellwig
2020-05-13 16:00 ` [PATCH 06/18] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 07/18] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 08/18] maccess: rename strnlen_unsafe_user to strnlen_user_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 09/18] maccess: remove probe_read_common and probe_write_common Christoph Hellwig
2020-05-13 16:00 ` [PATCH 10/18] maccess: unify the probe kernel arch hooks Christoph Hellwig
2020-05-14  1:13   ` Masami Hiramatsu
2020-05-19  5:46     ` Christoph Hellwig
2020-05-13 16:00 ` [PATCH 11/18] maccess: remove strncpy_from_unsafe Christoph Hellwig
2020-05-13 19:11   ` Linus Torvalds
2020-05-13 19:11     ` Linus Torvalds
2020-05-13 19:28     ` Christoph Hellwig
2020-05-13 22:36       ` Daniel Borkmann
2020-05-13 23:03         ` Linus Torvalds [this message]
2020-05-13 23:03           ` Linus Torvalds
2020-05-13 23:24           ` Daniel Borkmann
2020-05-13 23:20         ` Masami Hiramatsu
2020-05-13 23:59           ` Linus Torvalds
2020-05-13 23:59             ` Linus Torvalds
2020-05-14  1:00             ` Masami Hiramatsu
2020-05-14  2:43               ` Linus Torvalds
2020-05-14  2:43                 ` Linus Torvalds
2020-05-14  9:44                 ` Masami Hiramatsu
2020-05-14 10:27                   ` Daniel Borkmann
2020-05-13 23:28         ` Al Viro
2020-05-13 23:58           ` Daniel Borkmann
2020-05-14 10:01             ` David Laight
2020-05-14 10:21               ` Daniel Borkmann
2020-05-13 16:00 ` [PATCH 12/18] maccess: always use strict semantics for probe_kernel_read Christoph Hellwig
2020-05-13 16:00 ` [PATCH 13/18] maccess: move user access routines together Christoph Hellwig
2020-05-13 16:00 ` [PATCH 14/18] maccess: allow architectures to provide kernel probing directly Christoph Hellwig
2020-05-13 19:36   ` Linus Torvalds
2020-05-13 19:36     ` Linus Torvalds
2020-05-13 19:40     ` Christoph Hellwig
2020-05-13 19:48       ` Linus Torvalds
2020-05-13 19:48         ` Linus Torvalds
2020-05-13 19:54         ` Christoph Hellwig
2020-05-16  3:42   ` Masami Hiramatsu
2020-05-18 15:09     ` Christoph Hellwig
2020-05-13 16:00 ` [PATCH 15/18] x86: use non-set_fs based maccess routines Christoph Hellwig
2020-05-13 16:00 ` [PATCH 16/18] maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 17/18] maccess: rename probe_user_{read,write} to copy_{from,to}_user_nofault Christoph Hellwig
2020-05-13 16:00 ` [PATCH 18/18] maccess: rename probe_kernel_address to get_kernel_nofault Christoph Hellwig
2020-05-13 19:37 ` clean up and streamline probe_kernel_* and friends v2 Linus Torvalds
2020-05-13 19:37   ` Linus Torvalds
2020-05-13 23:04 ` Daniel Borkmann
2020-05-13 23:20   ` Linus Torvalds
2020-05-13 23:20     ` Linus Torvalds
2020-05-19  5:50   ` Christoph Hellwig

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