From: Pavel Machek <pavel@ucw.cz>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -mm] swsusp: userland interface (rev 2)
Date: Wed, 25 Jan 2006 13:18:48 +0100 [thread overview]
Message-ID: <20060125121848.GA1900@elf.ucw.cz> (raw)
In-Reply-To: <200601250035.39383.rjw@sisk.pl>
Hi!
> > > + case SNAPSHOT_ATOMIC_RESTORE:
> > > + if (data->mode != O_WRONLY || !data->frozen ||
> > > + !snapshot_image_loaded(&data->handle)) {
> > > + error = -EPERM;
> > > + break;
> > > + }
> > > + down(&pm_sem);
> > > + pm_prepare_console();
> > > + error = device_suspend(PMSG_FREEZE);
> > > + if (!error) {
> > > + mb();
> > > + error = swsusp_resume();
> > > + device_resume();
> > > + }
> >
> > whee, what does the mystery barrier do? It'd be nice to comment this
> > (please always comment open-coded barriers).
>
> Pavel should know. ;-)
Pavel does not known. That memory barrier should be part of assembly
parts, anyway, and AFAIK it is. Should be safe to kill.
> > > + case SNAPSHOT_GET_SWAP_PAGE:
> > > + if (!access_ok(VERIFY_WRITE, (unsigned long __user *)arg, _IOC_SIZE(cmd))) {
> > > + error = -EINVAL;
> > > + break;
> > > + }
> >
> > Why do we need an access_ok() here?
>
> Because we use __put_user() down the road?
>
> The problem is if the address is wrong we should not try to call
> alloc_swap_page() at all. If we did, we wouldn't be able to return the result
> and we would leak a swap page.
I think you need to watch for failing put_user and free the page at
that point. Anything else is racy as __put_user() may fail.
Pavel
--
Thanks, Sharp!
next prev parent reply other threads:[~2006-01-25 12:18 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-24 8:29 [PATCH -mm] swsusp: userland interface (rev 2) Rafael J. Wysocki
2006-01-24 11:14 ` Pavel Machek
2006-01-24 21:13 ` Andrew Morton
2006-01-24 21:30 ` Pavel Machek
2006-01-24 21:58 ` Andrew Morton
2006-01-24 22:14 ` Pavel Machek
2006-01-24 22:20 ` Dave Jones
2006-01-24 22:33 ` Pavel Machek
2006-01-24 22:38 ` Dave Jones
2006-01-24 22:44 ` Pavel Machek
2006-01-26 2:09 ` Jim Crilly
2006-01-26 7:58 ` Pavel Machek
2006-01-27 1:11 ` Greg KH
2006-01-27 3:42 ` Kay Sievers
2006-01-27 11:24 ` Rafael J. Wysocki
2006-01-24 22:47 ` Lee Revell
2006-01-24 23:53 ` Rafael J. Wysocki
2006-01-25 0:17 ` Andrew Morton
2006-01-25 0:31 ` Rafael J. Wysocki
2006-01-24 23:35 ` Rafael J. Wysocki
2006-01-25 2:46 ` Benjamin LaHaise
2006-01-25 10:50 ` Rafael J. Wysocki
2006-01-25 12:18 ` Pavel Machek [this message]
2006-01-25 12:29 ` Rafael J. Wysocki
2006-01-25 12:20 ` Pavel Machek
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