Commit 40d48527 authored by Antonio Quartulli's avatar Antonio Quartulli
Browse files

ovpn: fix check for skb_to_sgvec_nomark() return value 



Depending on the data offset, skb_to_sgvec_nomark() may use
less scatterlist elements than what was forecasted by the
previous call to skb_cow_data().

It specifically happens when 'skbheadlen(skb) < offset', because
in this case we entirely skip the skb's head, which would have
required its own scatterlist element.

For this reason, it doesn't make sense to check that
skb_to_sgvec_nomark() returns the same value as skb_cow_data(),
but we can rather check for errors only, as it happens in
other parts of the kernel.

Signed-off-by: default avatarAntonio Quartulli <antonio@openvpn.net>
parent 0ca74dfa

drivers/net/ovpn/crypto_aead.c

+12 −6
Original line number Diff line number Diff line
@@ -88,12 +88,15 @@ int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks, 


	/* build scatterlist to encrypt packet payload */

	ret = skb_to_sgvec_nomark(skb, sg + 1, 0, skb->len);

	if (unlikely(nfrags != ret))

		return -EINVAL;

	if (unlikely(ret < 0)) {

		netdev_err(peer->ovpn->dev,

			   "encrypt: cannot map skb to sg: %d\n", ret);

		return ret;

	}



	/* append auth_tag onto scatterlist */

	__skb_push(skb, tag_size);

	sg_set_buf(sg + nfrags + 1, skb->data, tag_size);

	sg_set_buf(sg + ret + 1, skb->data, tag_size);



	/* obtain packet ID, which is used both as a first

	 * 4 bytes of nonce and last 4 bytes of associated data.
@@ -201,11 +204,14 @@ int ovpn_aead_decrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks, 


	/* build scatterlist to decrypt packet payload */

	ret = skb_to_sgvec_nomark(skb, sg + 1, payload_offset, payload_len);

	if (unlikely(nfrags != ret))

		return -EINVAL;

	if (unlikely(ret < 0)) {

		netdev_err(peer->ovpn->dev,

			   "decrypt: cannot map skb to sg: %d\n", ret);

		return ret;

	}



	/* append auth_tag onto scatterlist */

	sg_set_buf(sg + nfrags + 1, skb->data + OVPN_AAD_SIZE, tag_size);

	sg_set_buf(sg + ret + 1, skb->data + OVPN_AAD_SIZE, tag_size);



	/* iv may be required by async crypto */

	ovpn_skb_cb(skb)->iv = kmalloc(OVPN_NONCE_SIZE, GFP_ATOMIC);