linux-kernel - Re: USBFS Memory allocation Bug

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 10 Mar 2010 10:16:09 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Mel Gorman <mel@....ul.ie>
cc:	Markus Rechberger <mrechberger@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, Greg KH <greg@...ah.com>
Subject: Re: USBFS Memory allocation Bug

On Wed, 10 Mar 2010, Mel Gorman wrote:

> On Tue, Mar 09, 2010 at 10:09:57PM +0100, Markus Rechberger wrote:
> > Hi,
> > 
> > I just stumbled around following issue:
> > 
> > <SNIP to have one full message>
> >
> > [275835.491094] mediasrv: page allocation failure. order:6, mode:0x40d0
> 
> This is massive. Why is usbdev_ioctl requiring an order-6 allocation?
> Does it have the option to fall back to vmalloc() for example?

We needed to implement an upper limit on the buffer size, and the value
chosen was sufficient for 8 ms of data.  There is no fallback to
vmalloc().

Of course, the mediasrv program could always make multiple smaller
data submissions instead of a single big one.

> So, it's a high-order allocation but no swap is configured. As the
> system has a big mix of both anonymous and file memory, it is likely it
> was unable to find a large enough contiguous range of file-backed memory
> it could discard. There is pretty much nothing the memory manager could
> do here. 
> 
> FWIW, if swap was configured I'd think there was more the memory manager
> could have done.
> 
> Is usb falling back to vmalloc() or order-0 pages possible?

No.  It's not possible since the buffer has to be contiguous for DMA
purposes (this is a requirement of the driver interface).

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/