From: Michal Hocko <mhocko@kernel.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrey Konovalov <andreyknvl@google.com>,
Felipe Balbi <balbi@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Deepa Dinamani <deepa.kernel@gmail.com>,
Mathieu Laurendeau <mat.lau@laposte.net>, Bin Liu <b-liu@ti.com>,
USB list <linux-usb@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller <syzkaller@googlegroups.com>,
Dmitry Vyukov <dvyukov@google.com>,
Kostya Serebryany <kcc@google.com>,
Cristopher Lameter <cl@linux.com>
Subject: Re: usb/gadget: warning in ep_write_iter/__alloc_pages_nodemask
Date: Wed, 14 Dec 2016 17:18:23 +0100 [thread overview]
Message-ID: <20161214161823.GQ25573@dhcp22.suse.cz> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1612141100280.2114-100000@iolanthe.rowland.org>
On Wed 14-12-16 11:13:11, Alan Stern wrote:
> On Wed, 14 Dec 2016, Michal Hocko wrote:
>
> > On Tue 13-12-16 08:33:34, Alan Stern wrote:
> > > On Tue, 13 Dec 2016, Michal Hocko wrote:
[...]
> > > > Well, my point was that it is not really hard to imagine to deplete
> > > > larger contiguous memory blocks (say PAGE_ALLOC_COSTLY_ORDER). Those are
> > > > still causing the OOM killer and chances are that a controlled flood of
> > > > these requests could completely DoS the system.
> > >
> > > Putting a limit on the total size of a single transfer would prevent
> > > this.
> >
> > Dunno, putting a limit to the user visible interface sounds wrong to me.
>
> In practice, I think the data transfer sizes tend to be not very large.
> But I could be wrong about that.
That is one part the other is whether a malicious user can abuse this to
DoS the kernel which is the point I am trying to make here. Depleting
non-costly high orders can be quite dangerious so allowing a free ticket
to them to arbitrary user in an arbitrary amount is definitely not good.
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2016-12-14 16:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-12 20:31 usb/gadget: warning in ep_write_iter/__alloc_pages_nodemask Andrey Konovalov
2016-12-12 20:32 ` Andrey Konovalov
2016-12-12 21:00 ` Alan Stern
2016-12-12 21:05 ` Michal Hocko
2016-12-12 21:12 ` Alan Stern
2016-12-13 8:04 ` Michal Hocko
2016-12-13 13:33 ` Alan Stern
2016-12-14 9:10 ` Michal Hocko
2016-12-14 16:13 ` Alan Stern
2016-12-14 16:18 ` Michal Hocko [this message]
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