linux-kernel - Re: [PATCH RFC] uaccess: user_access_begin_after_access

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Date:   Thu, 4 Jun 2020 16:03:35 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Jason Wang <jasowang@...hat.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH RFC] uaccess: user_access_begin_after_access_ok()

On Thu, Jun 04, 2020 at 06:10:23AM -0400, Michael S. Tsirkin wrote:

> 	stac()
> 	for (i = 0; i < 64; ++i) {
> 	 get_user(flags, desc[i].flags)
unsafe_get_user(), please.
> 	 smp_rmb()
> 	 if (!(flags & VALID))
> 		break;
> 	 copy_from_user(&adesc[i], desc + i, sizeof adesc[i]);
... and that would raw_copy_from_user() (or unsafe_copy_from_user(),
for wrapper that would take a label to bugger off to)
> 	}
> 	clac()