From: "Michael S. Tsirkin" <mst@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: mark.rutland@arm.com, Kees Cook <keescook@chromium.org>,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
bijan.mottahedeh@oracle.com, gedwards@ddn.com, joe@perches.com,
lenaic@lhuard.fr, liang.z.li@intel.com, mhocko@kernel.org,
mhocko@suse.com, stefanha@redhat.com, wei.w.wang@intel.com,
jasowang@redhat.com
Subject: Re: [PULL] vhost: cleanups and fixes
Date: Fri, 2 Nov 2018 13:21:06 -0400 [thread overview]
Message-ID: <20181102131334-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAHk-=wibzqo7C+mS+BgZxRbgdWe2w5F39EhuFUhZUxvotoGLuA@mail.gmail.com>
On Fri, Nov 02, 2018 at 10:10:45AM -0700, Linus Torvalds wrote:
> On Fri, Nov 2, 2018 at 9:59 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > Just for completeness I'd like to point out for vhost the copies are
> > done from the kernel thread. So yes we can switch to copy_to/from_user
> > but for e.g. 32-bit userspace running on top of a 64 bit kernel it is
> > IIUC not sufficient - we must *also* do access_ok checks on control path
> > when addresses are passed to the kernel and when current points to the
> > correct task struct.
>
> Don't you take over the VM with "use_mm()" when you do the copies?
Yes we do.
> So
> yes, it's a kernel thread, but it has a user VM, and though that
> should have the user limits.
>
> No?
>
> Linus
Here's what I meant: we have
#define access_ok(type, addr, size) \
({ \
WARN_ON_IN_IRQ(); \
likely(!__range_not_ok(addr, size, user_addr_max())); \
})
and
#define user_addr_max() (current->thread.addr_limit.seg)
it seems that it depends on current not on the active mm.
get_user and friends are similar:
ENTRY(__get_user_1)
mov PER_CPU_VAR(current_task), %_ASM_DX
cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX
jae bad_get_user
sbb %_ASM_DX, %_ASM_DX /* array_index_mask_nospec() */
and %_ASM_DX, %_ASM_AX
ASM_STAC
1: movzbl (%_ASM_AX),%edx
xor %eax,%eax
ASM_CLAC
ret
ENDPROC(__get_user_1)
EXPORT_SYMBOL(__get_user_1)
--
MST
next prev parent reply other threads:[~2018-11-02 17:21 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 21:19 [PULL] vhost: cleanups and fixes Michael S. Tsirkin
2018-11-01 21:44 ` Linus Torvalds
2018-11-01 23:00 ` Kees Cook
2018-11-01 23:06 ` Linus Torvalds
2018-11-01 23:55 ` Michael S. Tsirkin
2018-11-02 11:46 ` Mark Rutland
2018-11-02 13:04 ` Michael S. Tsirkin
2018-11-02 16:14 ` Linus Torvalds
2018-11-02 16:59 ` Michael S. Tsirkin
2018-11-02 17:10 ` Linus Torvalds
2018-11-02 17:15 ` Linus Torvalds
2018-11-02 19:01 ` Al Viro
2018-11-02 17:21 ` Michael S. Tsirkin [this message]
2018-11-02 18:02 ` Linus Torvalds
2018-11-02 18:12 ` Michael S. Tsirkin
2018-11-30 13:44 ` Michael S. Tsirkin
2018-11-30 19:01 ` Bijan Mottahedeh
2018-11-30 19:55 ` Michael S. Tsirkin
2018-11-01 23:38 ` Michael S. Tsirkin
[not found] <20200210010252-mutt-send-email-mst@kernel.org>
2020-02-11 2:07 ` Linus Torvalds
-- strict thread matches above, loose matches on Subject: below --
2019-10-15 21:19 Michael S. Tsirkin
2019-10-15 22:25 ` pr-tracker-bot
2019-05-14 21:11 Michael S. Tsirkin
2019-05-14 21:20 ` pr-tracker-bot
2018-06-11 16:23 Michael S. Tsirkin
2018-06-11 18:32 ` Linus Torvalds
2018-06-11 18:44 ` Linus Torvalds
2018-06-12 1:36 ` Michael S. Tsirkin
2018-06-12 1:59 ` Linus Torvalds
2018-06-12 11:05 ` Wei Wang
2018-06-14 15:01 ` Nitesh Narayan Lal
2018-06-15 3:53 ` Wei Wang
2018-06-12 1:57 ` Michael S. Tsirkin
2017-12-08 15:47 Michael S. Tsirkin
2017-12-04 13:25 Michael S. Tsirkin
2017-08-25 18:47 Michael S. Tsirkin
2017-04-10 21:36 Michael S. Tsirkin
2017-03-02 5:49 Michael S. Tsirkin
2017-02-03 21:43 Michael S. Tsirkin
2017-01-23 15:05 Michael S. Tsirkin
2017-01-23 21:50 ` Linus Torvalds
2017-01-24 2:45 ` Michael S. Tsirkin
2016-05-24 11:57 Michael S. Tsirkin
2015-12-21 7:58 Michael S. Tsirkin
2015-12-07 17:07 Michael S. Tsirkin
2015-09-18 10:42 Michael S. Tsirkin
2015-09-09 9:15 Michael S. Tsirkin
2015-07-28 10:00 Michael S. Tsirkin
2015-07-15 10:50 Michael S. Tsirkin
2015-07-15 11:26 ` Michael S. Tsirkin
2015-06-01 19:18 Michael S. Tsirkin
2015-06-01 19:45 ` Michael S. Tsirkin
2015-01-08 7:51 Michael S. Tsirkin
2015-01-01 12:26 Michael S. Tsirkin
2014-12-18 10:46 Michael S. Tsirkin
2014-11-13 21:22 Michael S. Tsirkin
2014-06-25 11:05 Michael S. Tsirkin
2013-07-15 18:31 Michael S. Tsirkin
2013-07-22 8:07 ` Michael S. Tsirkin
2013-07-08 11:45 Michael S. Tsirkin
2013-05-02 10:53 Michael S. Tsirkin
2013-05-02 18:55 ` Nicholas A. Bellinger
2013-05-02 19:33 ` Michael S. Tsirkin
2013-05-02 19:49 ` Linus Torvalds
2013-06-05 15:53 ` Michael S. Tsirkin
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