From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261945AbULGVe1 (ORCPT ); Tue, 7 Dec 2004 16:34:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261949AbULGVe1 (ORCPT ); Tue, 7 Dec 2004 16:34:27 -0500 Received: from ns.virtualhost.dk ([195.184.98.160]:34194 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S261945AbULGVdL (ORCPT ); Tue, 7 Dec 2004 16:33:11 -0500 Date: Tue, 7 Dec 2004 22:32:17 +0100 From: Jens Axboe To: Jesper Juhl Cc: linux-kernel , Katrina Tsipenyuk , katrina@fortifysoftware.com, Mark Hemment , akpm@osdl.org Subject: Re: [PATCH][2/2] fix unchecked returns from kmalloc() (in mm/slab.c) Message-ID: <20041207213216.GE10083@suse.de> References: <20041207212603.GC10083@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 07 2004, Jesper Juhl wrote: > On Tue, 7 Dec 2004, Jens Axboe wrote: > > > On Tue, Dec 07 2004, Jesper Juhl wrote: > > > > > > Problem reported by Katrina Tsipenyuk and the Fortify Software engineering > > > team in thread with subject "PROBLEM: unchecked returns from kmalloc() in > > > linux-2.6.10-rc2". > > > > > > Unfortunately I'm not very familliar with the code in question, and since > > > I didn't find a really good way to deal with a failing kmalloc() here I > > > settled for second best which is to add a BUG_ON() in case kmalloc fails. > > > This will at least crash in a sane way at the point the problem occoures > > > rather than getting strange problems at a (possibly) later time. If > > > someone who's familliar with how this code works has a better solution > > > then please step forward :) but in the mean time I think this is at least > > > a slight improvement over the current situation. > > > > > > Patch has been compile tested and boot tested and didn't blow up > > > instantly, but please review before applying. > > > > > > > > > Signed-off-by: Jesper Juhl > > > > > > diff -up linux-2.6.10-rc3-bk2-orig/mm/slab.c linux-2.6.10-rc3-bk2/mm/slab.c > > > --- linux-2.6.10-rc3-bk2-orig/mm/slab.c 2004-12-06 22:24:56.000000000 +0100 > > > +++ linux-2.6.10-rc3-bk2/mm/slab.c 2004-12-07 21:27:20.000000000 +0100 > > > @@ -804,6 +804,7 @@ void __init kmem_cache_init(void) > > > void * ptr; > > > > > > ptr = kmalloc(sizeof(struct arraycache_init), GFP_KERNEL); > > > + BUG_ON(ptr == NULL); /* FIXME: Can a failed kmalloc be handled better? */ > > > local_irq_disable(); > > > BUG_ON(ac_data(&cache_cache) != &initarray_cache.cache); > > > memcpy(ptr, ac_data(&cache_cache), sizeof(struct arraycache_init)); > > > > This is pointless, as a NULL deref on memcpy will give you the exact > > same info. > > > Hmm, now why didn't I think of that. Thanks Jens. > I guess I'm not up to the task of fixing this one. I'll try looking > harder, but I don't think I can do better in this case. See my next mail, I'm not so sure there's anything worth fixing. If there was no fear of it being misused, perhaps GFP_PANIC would be a proper way to flag that this really should not fail. -- Jens Axboe