From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [bpf-next PATCH] bpf: sockhash fix race with bpf_tcp_close and map delete Date: Mon, 28 May 2018 17:48:11 +0200 Message-ID: References: <20180525173712.4004.70590.stgit@john-Precision-Tower-5810> <9cae9278-fd9f-f90a-ca35-e2d4b3e63fe8@iogearbox.net> <35940fbd-c354-e5ad-8baf-678d8245389c@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: John Fastabend , ast@kernel.org Return-path: Received: from www62.your-server.de ([213.133.104.62]:40088 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1034800AbeE1PsN (ORCPT ); Mon, 28 May 2018 11:48:13 -0400 In-Reply-To: <35940fbd-c354-e5ad-8baf-678d8245389c@gmail.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 05/28/2018 05:13 PM, John Fastabend wrote: > On 05/27/2018 03:36 PM, Daniel Borkmann wrote: >> On 05/25/2018 07:37 PM, John Fastabend wrote: >>> syzbot reported two related splats, a use after free and null >>> pointer dereference, when a TCP socket is closed while the map is >>> also being removed. >>> >>> The psock keeps a reference to all map slots that have a reference >>> to the sock so that when the sock is closed we can clean up any >>> outstanding sock{map|hash} entries. This avoids pinning a sock >>> forever if the map owner fails to do proper cleanup. However, the >>> result is we have two paths that can free an entry in the map. Even >>> the comment in the sock{map|hash} tear down function, sock_hash_free() >>> notes this: >>> >>> At this point no update, lookup or delete operations can happen. >>> However, be aware we can still get a socket state event updates, >>> and data ready callbacks that reference the psock from sk_user_data. >>> >>> Both removal paths omitted taking the hash bucket lock resulting >>> in the case where we have two references that are in the process >>> of being free'd. >>> >>> Reported-by: syzbot+a761b81c211794fa1072@syzkaller.appspotmail.com >>> Signed-off-by: John Fastabend >> >> Applied to bpf-next, thanks John! > > This needs a v2 it introduces a slightly different/related error. I'll > have a v2 shortly. Ok, I've just dropped it from the tree in favor for a v2. Thanks John!