From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: [PATCH net] netlink: Relax attr validation for fixed length types Date: Tue, 5 Dec 2017 12:55:40 -0700 Message-ID: <20171205195540.41822-1-dsahern@gmail.com> Cc: David Ahern To: netdev@vger.kernel.org Return-path: Received: from mail-pf0-f195.google.com ([209.85.192.195]:38763 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751904AbdLETzr (ORCPT ); Tue, 5 Dec 2017 14:55:47 -0500 Received: by mail-pf0-f195.google.com with SMTP id u25so946615pfg.5 for ; Tue, 05 Dec 2017 11:55:47 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: Commit 28033ae4e0f5 ("net: netlink: Update attr validation to require exact length for some types") requires attributes using types NLA_U* and NLA_S* to have an exact length. This change is exposing bugs in various userspace commands that are sending attributes with an invalid length (e.g., attribute has type NLA_U8 and userspace sends NLA_U32). While the commands are clearly broken and need to be fixed, users are arguing that the sudden change in enforcement is breaking older commands on newer kernels for use cases that otherwise "worked". Relax the validation to print a warning mesage similar to what is done for messages containing extra bytes after parsing. Fixes: 28033ae4e0f5 ("net: netlink: Update attr validation to require exact length for some types") Signed-off-by: David Ahern --- lib/nlattr.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/lib/nlattr.c b/lib/nlattr.c index 8bf78b4b78f0..6122662906c8 100644 --- a/lib/nlattr.c +++ b/lib/nlattr.c @@ -28,8 +28,16 @@ static const u8 nla_attr_len[NLA_TYPE_MAX+1] = { }; static const u8 nla_attr_minlen[NLA_TYPE_MAX+1] = { + [NLA_U8] = sizeof(u8), + [NLA_U16] = sizeof(u16), + [NLA_U32] = sizeof(u32), + [NLA_U64] = sizeof(u64), [NLA_MSECS] = sizeof(u64), [NLA_NESTED] = NLA_HDRLEN, + [NLA_S8] = sizeof(s8), + [NLA_S16] = sizeof(s16), + [NLA_S32] = sizeof(s32), + [NLA_S64] = sizeof(s64), }; static int validate_nla_bitfield32(const struct nlattr *nla, @@ -70,10 +78,9 @@ static int validate_nla(const struct nlattr *nla, int maxtype, BUG_ON(pt->type > NLA_TYPE_MAX); /* for data types NLA_U* and NLA_S* require exact length */ - if (nla_attr_len[pt->type]) { - if (attrlen != nla_attr_len[pt->type]) - return -ERANGE; - return 0; + if (nla_attr_len[pt->type] && attrlen != nla_attr_len[pt->type]) { + pr_warn_ratelimited("netlink: '%s': attribute type %d has an invalid length.\n", + current->comm, type); } switch (pt->type) { -- 2.11.0