linux-kernel - Re: [patch 6/7 -mm] oom: avoid oom killer for lowmem allocations

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]

Message-ID: <alpine.DEB.2.00.1002151355000.26927@chino.kir.corp.google.com>
Date:	Mon, 15 Feb 2010 14:01:17 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Lubos Lunak <l.lunak@...e.cz>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [patch 6/7 -mm] oom: avoid oom killer for lowmem allocations

On Mon, 15 Feb 2010, KAMEZAWA Hiroyuki wrote:

> > I can't agree with that assessment, I don't think it's a desired result to 
> > ever panic the machine regardless of what /proc/sys/vm/panic_on_oom is set 
> > to because a lowmem page allocation fails especially considering, as 
> > mentioned in the changelog, these allocations are never __GFP_NOFAIL and 
> > returning NULL is acceptable.
> > 
> please add
>   WARN_ON((high_zoneidx < ZONE_NORMAL) && (gfp_mask & __GFP_NOFAIL))
> somewhere. Then, it seems your patch makes sense.
> 

high_zoneidx < ZONE_NORMAL is not the only case where this exists: it 
exists for __GFP_NOFAIL allocations that are not __GFP_FS as well and has 
for years, no special handling is now needed.

There should be no cases of either (GFP_DMA | __GFP_NOFAIL, or
GFP_NOFS | __GFP_NOFAIL) in my audit of the kernel code.  And since 
__GFP_NOFAIL is not to be added anymore (see Andrew's dab48dab), there's 
no real reason to add a WARN_ON() here.

> I don't like the "possibility" of inifinte loops.
> 

The possibility of infinite loops has always existed in the page allocator 
for __GFP_NOFAIL allocations, that's precisely why it's deprecated and 
eventually we seek to remove it.
--
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/