From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:40956 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934628AbeCGTlM (ORCPT ); Wed, 7 Mar 2018 14:41:12 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Roman Kapl , Jiri Pirko , Cong Wang , "David S. Miller" Subject: [PATCH 4.15 048/122] net: sched: report if filter is too large to dump Date: Wed, 7 Mar 2018 11:37:40 -0800 Message-Id: <20180307191735.949703125@linuxfoundation.org> In-Reply-To: <20180307191729.190879024@linuxfoundation.org> References: <20180307191729.190879024@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Roman Kapl [ Upstream commit 5ae437ad5a2ed573b1ebb04e0afa70b8869f88dd ] So far, if the filter was too large to fit in the allocated skb, the kernel did not return any error and stopped dumping. Modify the dumper so that it returns -EMSGSIZE when a filter fails to dump and it is the first filter in the skb. If we are not first, we will get a next chance with more room. I understand this is pretty near to being an API change, but the original design (silent truncation) can be considered a bug. Note: The error case can happen pretty easily if you create a filter with 32 actions and have 4kb pages. Also recent versions of iproute try to be clever with their buffer allocation size, which in turn leads to Signed-off-by: Roman Kapl Acked-by: Jiri Pirko Acked-by: Cong Wang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/sched/cls_api.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -1054,13 +1054,18 @@ static int tc_dump_tfilter(struct sk_buf nla_get_u32(tca[TCA_CHAIN]) != chain->index) continue; if (!tcf_chain_dump(chain, q, parent, skb, cb, - index_start, &index)) + index_start, &index)) { + err = -EMSGSIZE; break; + } } cb->args[0] = index; out: + /* If we did no progress, the error (EMSGSIZE) is real */ + if (skb->len == 0 && err) + return err; return skb->len; }