From: Michael Ellerman <mpe@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 6/6] powerpc: Implement user_access_begin and friends
Date: Thu, 23 Jan 2020 23:31:03 +1100 [thread overview]
Message-ID: <87ftg6icc8.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <87iml2idi9.fsf@mpe.ellerman.id.au>
Michael Ellerman <mpe@ellerman.id.au> writes:
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>> Today, when a function like strncpy_from_user() is called,
>> the userspace access protection is de-activated and re-activated
>> for every word read.
>>
>> By implementing user_access_begin and friends, the protection
>> is de-activated at the beginning of the copy and re-activated at the
>> end.
>>
>> Implement user_access_begin(), user_access_end() and
>> unsafe_get_user(), unsafe_put_user() and unsafe_copy_to_user()
>>
>> For the time being, we keep user_access_save() and
>> user_access_restore() as nops.
>
> That means we will run with user access enabled in a few more places, but
> it's only used sparingly AFAICS:
>
> kernel/trace/trace_branch.c: unsigned long flags = user_access_save();
> lib/ubsan.c: unsigned long flags = user_access_save();
> lib/ubsan.c: unsigned long ua_flags = user_access_save();
> mm/kasan/common.c: unsigned long flags = user_access_save();
>
> And we don't have objtool checking that user access enablement isn't
> leaking in the first place, so I guess it's OK for us not to implement
> these to begin with?
It looks like we can implement them on on all three KUAP
implementations.
For radix and 8xx we just return/set the relevant SPR.
For book3s/32/kup.h I think we'd just need to add a KUAP_CURRENT case to
allow_user_access()?
cheers
next prev parent reply other threads:[~2020-01-23 12:31 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-22 17:52 [PATCH v2 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin() Christophe Leroy
2020-01-22 17:52 ` [PATCH v2 2/6] powerpc/32s: Fix bad_kuap_fault() Christophe Leroy
2020-01-22 17:52 ` [PATCH v2 3/6] powerpc/kuap: Fix set direction in allow/prevent_user_access() Christophe Leroy
2020-01-22 17:52 ` [PATCH v2 4/6] powerpc/32s: Drop NULL addr verification Christophe Leroy
2020-01-22 17:52 ` [PATCH v2 5/6] powerpc/32s: prepare prevent_user_access() for user_access_end() Christophe Leroy
2020-01-23 10:59 ` Michael Ellerman
2020-01-22 17:52 ` [PATCH v2 6/6] powerpc: Implement user_access_begin and friends Christophe Leroy
2020-01-23 12:05 ` Michael Ellerman
2020-01-23 12:31 ` Michael Ellerman [this message]
2020-01-24 11:40 ` Christophe Leroy
[not found] ` <CAHk-=wgNQ-rWoLg0OCJYYYbKBnRAUK4NPU-OD+vv-6fWnd=8kA@mail.gmail.com>
2020-01-22 20:00 ` [PATCH v2 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin() Linus Torvalds
2020-01-22 20:15 ` Linus Torvalds
2020-01-22 20:37 ` Linus Torvalds
2020-01-23 6:27 ` Christophe Leroy
2020-01-23 11:56 ` Michael Ellerman
2020-01-23 12:00 ` Michael Ellerman
2020-01-23 12:43 ` Christophe Leroy
2020-01-23 18:38 ` Linus Torvalds
2020-01-24 10:42 ` Michael Ellerman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87ftg6icc8.fsf@mpe.ellerman.id.au \
--to=mpe@ellerman.id.au \
--cc=benh@kernel.crashing.org \
--cc=christophe.leroy@c-s.fr \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).