Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752342Ab3D2PMA (ORCPT ); Mon, 29 Apr 2013 11:12:00 -0400 Received: from a9-74.smtp-out.amazonses.com ([54.240.9.74]:34853 "EHLO a9-74.smtp-out.amazonses.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750792Ab3D2PL7 (ORCPT ); Mon, 29 Apr 2013 11:11:59 -0400 X-Greylist: delayed 761 seconds by postgrey-1.27 at vger.kernel.org; Mon, 29 Apr 2013 11:11:59 EDT Date: Mon, 29 Apr 2013 14:59:16 +0000 From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Glauber Costa cc: Pekka Enberg , Tetsuo Handa , LKML Subject: Re: [linux-next-20130422] Bug in SLAB? In-Reply-To: <517E8758.9040803@parallels.com> Message-ID: <0000013e564e0e5a-121c52f9-e489-470f-99d5-67a5ad42eb75-000000@email.amazonses.com> References: <201304242108.FDC35910.VJMHFFFSOLOOQt@I-love.SAKURA.ne.jp> <201304252120.GII21814.FMJFtHLOOVQFOS@I-love.SAKURA.ne.jp> <201304291140.IFJ95894.OFLSFFHQOOMVJt@I-love.SAKURA.ne.jp> <517E8758.9040803@parallels.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Content-ID: X-SES-Outgoing: 2013.04.29-54.240.9.74 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1164 Lines: 32 On Mon, 29 Apr 2013, Glauber Costa wrote: > >> causes no warning at compile time and returns NULL at runtime. But > >> > >> unsigned int size = 8 * 1024 * 1024; > >> kmalloc(size, GFP_KERNEL); > >> > >> causes compile time warning > >> > >> include/linux/slab_def.h:136: warning: array subscript is above array bounds > >> > >> and runtime bug. SLAB should have support up to 2 << 25 = 1 mb << 5 = 32M > I believe this is because the code now always assume that the cache is > found when a constant is passed. Before this patch, we had a "found" > statement that was mistakenly removed. The code in kmalloc_index() creates a BUG() and preferentially should create a compile time failure when a number that is too big is passed to it. What is MAX_ORDER on the architecture? An allocation size of more than MAX_ORDER is not supported by the page allocator or by slab. It is safe to return NULL in that case. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/