From: Sowmini Varadhan Subject: Re: [PATCH net-next 2/2] xfrm: Fix unaligned access in xfrm_notify_sa() for DELSA Date: Wed, 21 Oct 2015 08:36:28 -0400 Message-ID: <20151021123628.GP6948@oracle.com> References: <65f37efeff5af105c89493dda4f38c61e4cd495f.1445286755.git.sowmini.varadhan@oracle.com> <20151021065704.GM7701@secunet.com> <20151021105442.GM6948@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, herbert@gondor.apana.org.au, dhowells@redhat.com, davem@davemloft.net, zohar@linux.vnet.ibm.com, David.Woodhouse@intel.com To: Steffen Klassert Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:27218 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751701AbbJUMgy (ORCPT ); Wed, 21 Oct 2015 08:36:54 -0400 Content-Disposition: inline In-Reply-To: <20151021105442.GM6948@oracle.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: On (10/21/15 06:54), Sowmini Varadhan wrote: > But __alignof__(*p) is 8 on sparc, and without the patch I get > all types of unaligned access. So what do you suggest as the fix? Even though the alignment is, in fact, 8 (and that comes from struct xfrm_lifetime_cfg), if uspace is firmly attached to the 4 byte alignment, I think we can retain that behavior and still avoid unaligned access in the kernel with the following (admittedly ugly hack). Can you please take a look? I tested it with 'ip x m' and a transport mode tunnel on my sparc. diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 158ef4a..ca4e7f0 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -2620,7 +2620,7 @@ static inline size_t xfrm_sa_len(struct xfrm_state *x) static int xfrm_notify_sa(struct xfrm_state *x, const struct km_event *c) { struct net *net = xs_net(x); - struct xfrm_usersa_info *p; + struct xfrm_usersa_info *p, tmp; struct xfrm_usersa_id *id; struct nlmsghdr *nlh; struct sk_buff *skb; @@ -2659,11 +2659,16 @@ static int xfrm_notify_sa(struct xfrm_state *x, const struct km_event *c) if (attr == NULL) goto out_free_skb; - p = PTR_ALIGN(nla_data(attr), __alignof__(*p)); + p = nla_data(attr); + err = copy_to_user_state_extra(x, &tmp, skb); + if (err) + goto out_free_skb; + memcpy((u8 *)p, &tmp, sizeof(tmp)); + } else { + err = copy_to_user_state_extra(x, p, skb); + if (err) + goto out_free_skb; } - err = copy_to_user_state_extra(x, p, skb); - if (err) - goto out_free_skb; nlmsg_end(skb, nlh);