From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Berg Subject: Re: [PATCH v2] netlink: do not proceed if dump's start() errs Date: Sat, 30 Sep 2017 08:56:10 +0200 Message-ID: <1506754570.3568.3.camel@sipsolutions.net> References: <20170927224144.1749-1-Jason@zx2c4.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit To: "Jason A. Donenfeld" , davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20170927224144.1749-1-Jason@zx2c4.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.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