From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) by kanga.kvack.org (Postfix) with ESMTP id BE5EE8E0001 for ; Fri, 21 Dec 2018 16:58:42 -0500 (EST) Received: by mail-pl1-f199.google.com with SMTP id ay11so4995744plb.20 for ; Fri, 21 Dec 2018 13:58:42 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id q5sor41526895pgv.82.2018.12.21.13.58.41 for (Google Transport Security); Fri, 21 Dec 2018 13:58:41 -0800 (PST) Date: Fri, 21 Dec 2018 13:58:39 -0800 (PST) From: David Rientjes Subject: Re: [PATCH RFC] mm: vmalloc: do not allow kzalloc to fail In-Reply-To: <1545337437-673-1-git-send-email-hofrat@osadl.org> Message-ID: References: <1545337437-673-1-git-send-email-hofrat@osadl.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Nicholas Mc Guire Cc: Andrew Morton , Chintan Pandya , Michal Hocko , Andrey Ryabinin , Arun KS , Joe Perches , "Luis R. Rodriguez" , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, 20 Dec 2018, Nicholas Mc Guire wrote: > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 871e41c..1c118d7 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1258,7 +1258,7 @@ void __init vmalloc_init(void) > > /* Import existing vmlist entries. */ > for (tmp = vmlist; tmp; tmp = tmp->next) { > - va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT); > + va = kzalloc(sizeof(*va), GFP_NOWAIT | __GFP_NOFAIL); > va->flags = VM_VM_AREA; > va->va_start = (unsigned long)tmp->addr; > va->va_end = va->va_start + tmp->size; Hi Nicholas, You're right that this looks wrong because there's no guarantee that va is actually non-NULL. __GFP_NOFAIL won't help in init, unfortunately, since we're not giving the page allocator a chance to reclaim so this would likely just end up looping forever instead of crashing with a NULL pointer dereference, which would actually be the better result. You could do BUG_ON(!va); to make it obvious why we crashed, however. It makes it obvious that the crash is intentional rather than some error in the kernel code. 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Rodriguez" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] mm: vmalloc: do not allow kzalloc to fail In-Reply-To: <1545337437-673-1-git-send-email-hofrat@osadl.org> Message-ID: References: <1545337437-673-1-git-send-email-hofrat@osadl.org> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Message-ID: <20181221215839.u8Q0Zsy94BgzW1c3VrIgqY_tkZPdJ_ffru4KuTdzxuU@z> On Thu, 20 Dec 2018, Nicholas Mc Guire wrote: > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 871e41c..1c118d7 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1258,7 +1258,7 @@ void __init vmalloc_init(void) > > /* Import existing vmlist entries. */ > for (tmp = vmlist; tmp; tmp = tmp->next) { > - va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT); > + va = kzalloc(sizeof(*va), GFP_NOWAIT | __GFP_NOFAIL); > va->flags = VM_VM_AREA; > va->va_start = (unsigned long)tmp->addr; > va->va_end = va->va_start + tmp->size; Hi Nicholas, You're right that this looks wrong because there's no guarantee that va is actually non-NULL. __GFP_NOFAIL won't help in init, unfortunately, since we're not giving the page allocator a chance to reclaim so this would likely just end up looping forever instead of crashing with a NULL pointer dereference, which would actually be the better result. You could do BUG_ON(!va); to make it obvious why we crashed, however. It makes it obvious that the crash is intentional rather than some error in the kernel code.