From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sabrina Dubroca Subject: Re: [PATCH] macsec: dynamically allocate space for sglist Date: Tue, 25 Apr 2017 18:36:02 +0200 Message-ID: <20170425163602.GA17973@bistromath.localdomain> References: <20170425152300.3830-1-Jason@zx2c4.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: Netdev , LKML , David Miller , stable@vger.kernel.org, security@kernel.org To: "Jason A. Donenfeld" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:40178 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1430579AbdDYQgF (ORCPT ); Tue, 25 Apr 2017 12:36:05 -0400 Content-Disposition: inline In-Reply-To: <20170425152300.3830-1-Jason@zx2c4.com> Sender: netdev-owner@vger.kernel.org List-ID: 2017-04-25, 17:23:00 +0200, Jason A. Donenfeld wrote: > We call skb_cow_data, which is good anyway to ensure we can actually > modify the skb as such (another error from prior). Now that we have the > number of fragments required, we can safely allocate exactly that amount > of memory. > > Signed-off-by: Jason A. Donenfeld > Cc: Sabrina Dubroca > Cc: security@kernel.org > Cc: stable@vger.kernel.org > --- > drivers/net/macsec.c | 25 ++++++++++++++++++++----- > 1 file changed, 20 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c > index dbab05afcdbe..56dafdee4c9c 100644 > --- a/drivers/net/macsec.c > +++ b/drivers/net/macsec.c [...] > @@ -917,6 +926,7 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb, > { > int ret; > struct scatterlist *sg; > + struct sk_buff *trailer; > unsigned char *iv; > struct aead_request *req; > struct macsec_eth_header *hdr; > @@ -927,7 +937,12 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb, > if (!skb) > return ERR_PTR(-ENOMEM); > > - req = macsec_alloc_req(rx_sa->key.tfm, &iv, &sg); > + ret = skb_cow_data(skb, 0, &trailer); > + if (unlikely(ret < 0)) { > + kfree_skb(skb); > + return ERR_PTR(ret); > + } > + req = macsec_alloc_req(rx_sa->key.tfm, &iv, &sg, ret); > if (!req) { > kfree_skb(skb); > return ERR_PTR(-ENOMEM); There's a problem here (and in macsec_encrypt): you need to update the call to sg_init_table, like I did in my patch. Otherwise, sg_init_table() is going to access sg[MAX_SKB_FRAGS], which may be past what you allocated. How did you test this? ;) -- Sabrina