[PATCH v2] macsec: dynamically allocate space for sglist

From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Netdev <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	stable@vger.kernel.org, security@kernel.org,
	Sabrina Dubroca <sd@queasysnail.net>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: [PATCH v2] macsec: dynamically allocate space for sglist
Date: Tue, 25 Apr 2017 19:08:18 +0200	[thread overview]
Message-ID: <20170425170818.32661-1-Jason@zx2c4.com> (raw)
In-Reply-To: <20170425163602.GA17973@bistromath.localdomain>

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 <Jason@zx2c4.com>
Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: security@kernel.org
Cc: stable@vger.kernel.org
---
Changes v1 -> v2:
  - sg_init_table now takes the correct argument.

 drivers/net/macsec.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index dbab05afcdbe..49ce4e9f4a0f 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -617,7 +617,8 @@ static void macsec_encrypt_done(struct crypto_async_request *base, int err)
 
 static struct aead_request *macsec_alloc_req(struct crypto_aead *tfm,
 					     unsigned char **iv,
-					     struct scatterlist **sg)
+					     struct scatterlist **sg,
+					     int num_frags)
 {
 	size_t size, iv_offset, sg_offset;
 	struct aead_request *req;
@@ -629,7 +630,7 @@ static struct aead_request *macsec_alloc_req(struct crypto_aead *tfm,
 
 	size = ALIGN(size, __alignof__(struct scatterlist));
 	sg_offset = size;
-	size += sizeof(struct scatterlist) * (MAX_SKB_FRAGS + 1);
+	size += sizeof(struct scatterlist) * num_frags;
 
 	tmp = kmalloc(size, GFP_ATOMIC);
 	if (!tmp)
@@ -649,6 +650,7 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
 {
 	int ret;
 	struct scatterlist *sg;
+	struct sk_buff *trailer;
 	unsigned char *iv;
 	struct ethhdr *eth;
 	struct macsec_eth_header *hh;
@@ -723,7 +725,14 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
 		return ERR_PTR(-EINVAL);
 	}
 
-	req = macsec_alloc_req(tx_sa->key.tfm, &iv, &sg);
+	ret = skb_cow_data(skb, 0, &trailer);
+	if (unlikely(ret < 0)) {
+		macsec_txsa_put(tx_sa);
+		kfree_skb(skb);
+		return ERR_PTR(ret);
+	}
+
+	req = macsec_alloc_req(tx_sa->key.tfm, &iv, &sg, ret);
 	if (!req) {
 		macsec_txsa_put(tx_sa);
 		kfree_skb(skb);
@@ -732,7 +741,7 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
 
 	macsec_fill_iv(iv, secy->sci, pn);
 
-	sg_init_table(sg, MAX_SKB_FRAGS + 1);
+	sg_init_table(sg, ret);
 	skb_to_sgvec(skb, sg, 0, skb->len);
 
 	if (tx_sc->encrypt) {
@@ -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);
@@ -936,7 +951,7 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb,
 	hdr = (struct macsec_eth_header *)skb->data;
 	macsec_fill_iv(iv, sci, ntohl(hdr->packet_number));
 
-	sg_init_table(sg, MAX_SKB_FRAGS + 1);
+	sg_init_table(sg, ret);
 	skb_to_sgvec(skb, sg, 0, skb->len);
 
 	if (hdr->tci_an & MACSEC_TCI_E) {
@@ -2716,7 +2731,7 @@ static netdev_tx_t macsec_start_xmit(struct sk_buff *skb,
 }
 
 #define MACSEC_FEATURES \
-	(NETIF_F_SG | NETIF_F_HIGHDMA)
+	(NETIF_F_SG | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST)
 static struct lock_class_key macsec_netdev_addr_lock_key;
 
 static int macsec_dev_init(struct net_device *dev)
-- 
2.12.2
