From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752696AbdI3HhX (ORCPT ); Sat, 30 Sep 2017 03:37:23 -0400 Received: from s3.sipsolutions.net ([144.76.63.242]:54836 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751345AbdI3HhV (ORCPT ); Sat, 30 Sep 2017 03:37:21 -0400 X-Greylist: delayed 2461 seconds by postgrey-1.27 at vger.kernel.org; Sat, 30 Sep 2017 03:37:21 EDT Message-ID: <1506754570.3568.3.camel@sipsolutions.net> Subject: Re: [PATCH v2] netlink: do not proceed if dump's start() errs From: Johannes Berg To: "Jason A. Donenfeld" , davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Sat, 30 Sep 2017 08:56:10 +0200 In-Reply-To: <20170927224144.1749-1-Jason@zx2c4.com> References: <20170927224144.1749-1-Jason@zx2c4.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2017-09-28 at 00:41 +0200, Jason A. Donenfeld wrote: > Drivers that use the start method for netlink dumping rely on dumpit > not > being called if start fails. For example, ila_xlat.c allocates memory > and assigns it to cb->args[0] in its start() function. It might fail > to > do that and return -ENOMEM instead. However, even when returning an > error, dumpit will be called, which, in the example above, quickly > dereferences the memory in cb->args[0], which will OOPS the kernel. > This > is but one example of how this goes wrong. > > Since start() has always been a function with an int return type, it > therefore makes sense to use it properly, rather than ignoring it. > This > patch thus returns early and does not call dumpit() when start() > fails. > > Signed-off-by: Jason A. Donenfeld Reviewed-by: Johannes Berg FWIW, I found another (indirect, via genetlink, like ila_xlat.c) in- tree user that cares and expects the correct failure behaviour: net/ipv6/seg6.c .start  = seg6_genl_dumphmac_start, which can also have memory allocation failures. No others appear to exist, afaict. Either way, perhaps it's worth sending this to stable for that reason. johannes