From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757342Ab2C0Wvw (ORCPT ); Tue, 27 Mar 2012 18:51:52 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:46499 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756724Ab2C0Wvv (ORCPT ); Tue, 27 Mar 2012 18:51:51 -0400 Date: Tue, 27 Mar 2012 15:51:49 -0700 From: Andrew Morton To: Dave Jones Cc: viro@zeniv.linux.org.uk, Linux Kernel Subject: Re: suppress page allocation failure warnings from sys_listxattr Message-Id: <20120327155149.d41a235b.akpm@linux-foundation.org> In-Reply-To: <20120313182220.GA11500@redhat.com> References: <20120313182220.GA11500@redhat.com> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 13 Mar 2012 14:22:20 -0400 Dave Jones wrote: > This size is user controllable, and so it's trivial for someone to trigger a > stream of order:4 page allocation errors. > > Signed-off-by: Dave Jones > > --- > There's also a similar problem in setxattr, but I'm not sure how we want > to pass NOWARN down to memdup_user. Thoughts ? > > diff --git a/fs/xattr.c b/fs/xattr.c > index 82f4337..544df90 100644 > --- a/fs/xattr.c > +++ b/fs/xattr.c > @@ -496,7 +496,7 @@ listxattr(struct dentry *d, char __user *list, size_t size) > if (size) { > if (size > XATTR_LIST_MAX) > size = XATTR_LIST_MAX; > - klist = kmalloc(size, GFP_KERNEL); > + klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL); > if (!klist) > return -ENOMEM; > } hm. The patch is good, but one would hope that it isn't "trivial" to trigger a page allocation failure for a kmalloc(65536, GFP_KERNEL) - the VM is supposed to be able to handle that. Is it really *that* easy, or is Something Unusual happening with that machine?