linux-kernel - Re: suppress page allocation failure warnings from sys

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Date:	Wed, 28 Mar 2012 22:08:20 -0400
From:	Dave Jones <davej@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Joe Perches <joe@...ches.com>, Dave Chinner <david@...morbit.com>,
	viro@...iv.linux.org.uk,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: suppress page allocation failure warnings from sys_listxattr

On Wed, Mar 28, 2012 at 07:02:11PM -0700, Andrew Morton wrote:

 > > Also, what happens if something allocates
 > > and sits on a bunch of vmalloc'd memory ? would we start seeing oom kills ?
 > 
 > vmalloc() would fail.

Ok, that's a pretty boring failure mode, so not a big deal probably.

 > > (thinking of the context of my fuzzing tool where a bunch of instances could
 > >  feasibly call these syscalls and not sit on huge amounts per thread, but
 > >  collectively...  I'm wondering if it could be provoked into killing
 > >  processes I don't own)
 > 
 > umm, if you wanted to deliberately trigger a vmalloc() failure then I
 > guess a good approach would be to locate a vmalloc() site which can
 > persist beyond the syscall (modprobe is a good one!) then exercise it
 > in a way so that there are no N-byte holes left in the arena, then
 > trigger an N-byte vmalloc().

Well modprobe is root-only, so that's not so bad. But it looks like
key_add (see other thread from this evening) and probably others can be
called as a user and gobble up vmalloc space. omnomnom.

	Dave

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