From: "Michael S. Tsirkin" <mst@redhat.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jason Wang <jasowang@redhat.com>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH RFC] uaccess: user_access_begin_after_access_ok()
Date: Wed, 3 Jun 2020 02:25:56 -0400 [thread overview]
Message-ID: <20200603020325-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200603041849.GT23230@ZenIV.linux.org.uk>
On Wed, Jun 03, 2020 at 05:18:49AM +0100, Al Viro wrote:
> On Wed, Jun 03, 2020 at 11:57:11AM +0800, Jason Wang wrote:
>
> > > How widely do you hope to stretch the user_access areas, anyway?
> >
> >
> > To have best performance for small packets like 64B, if possible, we want to
> > disable STAC not only for the metadata access done by vhost accessors but
> > also the data access via iov iterator.
>
> If you want to try and convince Linus to go for that, make sure to Cc
> me on that thread. Always liked quality flame...
It's not about iov the way I see it.
It's a more fine-grained version of "nosmap".
Right now you basically want nosmap if you are running
a workload that does 100 byte reads/writes of userspace memory
all the time.
Which isn't so bad, I'm not sure how much security does smap add at all.
Were there any exploits that it blocked ever since it was introduced?
But in any case, it would be nice to also have an option to make it
possible to disable smap e.g. just for vhost. Not because vhost is
so secure, but simply because user wants this tradeoff.
--
MST
next prev parent reply other threads:[~2020-06-03 6:26 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-02 8:45 [PATCH RFC] uaccess: user_access_begin_after_access_ok() Michael S. Tsirkin
2020-06-02 10:15 ` Jason Wang
2020-06-02 16:33 ` Al Viro
2020-06-02 17:18 ` Linus Torvalds
2020-06-02 17:44 ` Al Viro
2020-06-02 17:46 ` Al Viro
2020-06-02 20:32 ` Michael S. Tsirkin
2020-06-02 20:41 ` David Laight
2020-06-02 21:58 ` Al Viro
2020-06-03 8:08 ` David Laight
2020-06-02 20:43 ` Linus Torvalds
2020-06-03 6:01 ` Michael S. Tsirkin
[not found] ` <CAHk-=wi3=QuD30fRq8fYYTj9WmkgeZ0VR_Sh3DQHU+nmwj-jMg@mail.gmail.com>
2020-06-03 16:59 ` Linus Torvalds
2020-06-02 16:30 ` Al Viro
2020-06-02 20:42 ` Michael S. Tsirkin
2020-06-02 22:10 ` Al Viro
2020-06-03 5:17 ` Michael S. Tsirkin
2020-06-03 1:48 ` Al Viro
2020-06-03 3:57 ` Jason Wang
2020-06-03 4:18 ` Al Viro
2020-06-03 5:18 ` Jason Wang
2020-06-03 5:46 ` Michael S. Tsirkin
2020-06-03 6:23 ` Jason Wang
2020-06-03 6:30 ` Michael S. Tsirkin
2020-06-03 6:36 ` Jason Wang
2020-06-04 16:49 ` Michael S. Tsirkin
2020-06-05 10:03 ` Jason Wang
2020-06-06 20:08 ` Michael S. Tsirkin
2020-06-03 6:25 ` Michael S. Tsirkin [this message]
2020-06-03 5:29 ` Michael S. Tsirkin
2020-06-03 16:52 ` Al Viro
2020-06-04 6:10 ` Jason Wang
2020-06-04 14:59 ` Al Viro
2020-06-04 16:46 ` Michael S. Tsirkin
2020-06-04 10:10 ` Michael S. Tsirkin
2020-06-04 15:03 ` Al Viro
2020-06-04 16:47 ` Michael S. Tsirkin
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=20200603020325-mutt-send-email-mst@kernel.org \
--to=mst@redhat.com \
--cc=jasowang@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=viro@zeniv.linux.org.uk \
/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).