linux-kernel - Re: USBFS Memory allocation Bug

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Message-ID: <Pine.LNX.4.44L0.1003100958250.1516-100000@iolanthe.rowland.org>
Date:	Wed, 10 Mar 2010 10:04:22 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Markus Rechberger <mrechberger@...il.com>
cc:	LKML <linux-kernel@...r.kernel.org>, Greg KH <greg@...ah.com>
Subject: Re: USBFS Memory allocation Bug

On Wed, 10 Mar 2010, Markus Rechberger wrote:

> > At any rate, clearly the bug, if there is one, lies in the memory
> > management subsystem and not in usbfs.
> >
> 
> seems like yes, but the final result of this is that mediasrv was not
> killable anymore.

You should have said so earlier.  That is indeed a serious bug.

> Shouldn't the syscall just fail if this happens?

It _does_ just fail if memory can't be allocated.  Here's the relevant 
code from proc_do_submiturb():

		as->urb->transfer_buffer = kmalloc(uurb->buffer_length,
				GFP_KERNEL);
		if (!as->urb->transfer_buffer) {
			kfree(isopkt);
			kfree(dr);
			free_async(as);
			return -ENOMEM;
		}

Where was the mediasrv process hung when you tried to kill it?

Alan Stern

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