From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-f193.google.com ([209.85.208.193]:44024 "EHLO mail-lj1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727937AbfFNNJs (ORCPT ); Fri, 14 Jun 2019 09:09:48 -0400 Received: by mail-lj1-f193.google.com with SMTP id 16so2320826ljv.10 for ; Fri, 14 Jun 2019 06:09:47 -0700 (PDT) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= Subject: Re: [PATCH bpf 1/3] devmap: Fix premature entry free on destroying map In-Reply-To: References: <20190614082015.23336-1-toshiaki.makita1@gmail.com> <20190614082015.23336-2-toshiaki.makita1@gmail.com> <877e9octre.fsf@toke.dk> <87sgscbc5d.fsf@toke.dk> Date: Fri, 14 Jun 2019 15:09:44 +0200 Message-ID: <87muikb9ev.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: xdp-newbies-owner@vger.kernel.org List-ID: To: Toshiaki Makita , Alexei Starovoitov , Daniel Borkmann , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend Cc: netdev@vger.kernel.org, xdp-newbies@vger.kernel.org, bpf@vger.kernel.org, "Michael S. Tsirkin" , Jason Wang , David Ahern Toshiaki Makita writes: > On 19/06/14 (金) 21:10:38, Toke Høiland-Jørgensen wrote: >> Toke Høiland-Jørgensen writes: >> >>> Toshiaki Makita writes: >>> >>>> dev_map_free() waits for flush_needed bitmap to be empty in order to >>>> ensure all flush operations have completed before freeing its entries. >>>> However the corresponding clear_bit() was called before using the >>>> entries, so the entries could be used after free. >>>> >>>> All access to the entries needs to be done before clearing the bit. >>>> It seems commit a5e2da6e9787 ("bpf: netdev is never null in >>>> __dev_map_flush") accidentally changed the clear_bit() and memory access >>>> order. >>>> >>>> Note that the problem happens only in __dev_map_flush(), not in >>>> dev_map_flush_old(). dev_map_flush_old() is called only after nulling >>>> out the corresponding netdev_map entry, so dev_map_free() never frees >>>> the entry thus no such race happens there. >>>> >>>> Fixes: a5e2da6e9787 ("bpf: netdev is never null in __dev_map_flush") >>>> Signed-off-by: Toshiaki Makita >>> >>> I recently posted a patch[0] that gets rid of the bitmap entirely, so I >>> think you can drop this one... >> >> Alternatively, since this entire series should probably go to stable, I >> can respin mine on top of it? > > Indeed conflict will happen, as this is for 'bpf' not 'bpf-next'. > Sorry for disturbing your work. Oh, no worries! > I'm also not sure how to proceed in this case. I guess we'll leave that up to the maintainers :) -Toke