sctp: add refcnt support for sh_key

With refcnt support for sh_key, chunks auth sh_keys can be decided
before enqueuing it. Changing the active key later will not affect
the chunks already enqueued.

Furthermore, this is necessary when adding the support for authinfo
for sendmsg in next patch.

Note that struct sctp_chunk can't be grown due to that performance
drop issue on slow cpu, so it just reuses head_skb memory for shkey
in sctp_chunk.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: lxin

include/net/sctp/auth.h

@@ -62,8 +62,9 @@ struct sctp_auth_bytes {
 /* Definition for a shared key, weather endpoint or association */
 struct sctp_shared_key {
 	struct list_head key_list;
-	__u16 key_id;
 	struct sctp_auth_bytes *key;
+	refcount_t refcnt;
+	__u16 key_id;
 };
 
 #define key_for_each(__key, __list_head) \
@@ -103,8 +104,10 @@ int sctp_auth_send_cid(enum sctp_cid chunk,
 int sctp_auth_recv_cid(enum sctp_cid chunk,
 		       const struct sctp_association *asoc);
 void sctp_auth_calculate_hmac(const struct sctp_association *asoc,
-			    struct sk_buff *skb,
-			    struct sctp_auth_chunk *auth, gfp_t gfp);
+			      struct sk_buff *skb, struct sctp_auth_chunk *auth,
+			      struct sctp_shared_key *ep_key, gfp_t gfp);
+void sctp_auth_shkey_release(struct sctp_shared_key *sh_key);
+void sctp_auth_shkey_hold(struct sctp_shared_key *sh_key);
 
 /* API Helpers */
 int sctp_auth_ep_add_chunkid(struct sctp_endpoint *ep, __u8 chunk_id);

include/net/sctp/sm.h

@@ -263,7 +263,8 @@ int sctp_process_asconf_ack(struct sctp_association *asoc,
 struct sctp_chunk *sctp_make_fwdtsn(const struct sctp_association *asoc,
 				    __u32 new_cum_tsn, size_t nstreams,
 				    struct sctp_fwdtsn_skip *skiplist);
-struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc);
+struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc,
+				  __u16 key_id);
 struct sctp_chunk *sctp_make_strreset_req(const struct sctp_association *asoc,
 					  __u16 stream_num, __be16 *stream_list,
 					  bool out, bool in);

include/net/sctp/structs.h

@@ -577,8 +577,12 @@ struct sctp_chunk {
 	/* This points to the sk_buff containing the actual data.  */
 	struct sk_buff *skb;
 
-	/* In case of GSO packets, this will store the head one */
-	struct sk_buff *head_skb;
+	union {
+		/* In case of GSO packets, this will store the head one */
+		struct sk_buff *head_skb;
+		/* In case of auth enabled, this will point to the shkey */
+		struct sctp_shared_key *shkey;
+	};
 
 	/* These are the SCTP headers by reverse order in a packet.
 	 * Note that some of these may happen more than once.  In that
@@ -1995,6 +1999,7 @@ struct sctp_association {
 	 * The current generated assocaition shared key (secret)
 	 */
 	struct sctp_auth_bytes *asoc_shared_key;
+	struct sctp_shared_key *shkey;
 
 	/* SCTP AUTH: hmac id of the first peer requested algorithm
 	 * that we support.

net/sctp/auth.c

@@ -101,20 +101,32 @@ struct sctp_shared_key *sctp_auth_shkey_create(__u16 key_id, gfp_t gfp)
 		return NULL;
 
 	INIT_LIST_HEAD(&new->key_list);
+	refcount_set(&new->refcnt, 1);
 	new->key_id = key_id;
 
 	return new;
 }
 
 /* Free the shared key structure */
-static void sctp_auth_shkey_free(struct sctp_shared_key *sh_key)
+static void sctp_auth_shkey_destroy(struct sctp_shared_key *sh_key)
 {
 	BUG_ON(!list_empty(&sh_key->key_list));
 	sctp_auth_key_put(sh_key->key);
 	sh_key->key = NULL;
 	kfree(sh_key);
 }
 
+void sctp_auth_shkey_release(struct sctp_shared_key *sh_key)
+{
+	if (refcount_dec_and_test(&sh_key->refcnt))
+		sctp_auth_shkey_destroy(sh_key);
+}
+
+void sctp_auth_shkey_hold(struct sctp_shared_key *sh_key)
+{
+	refcount_inc(&sh_key->refcnt);
+}
+
 /* Destroy the entire key list.  This is done during the
  * associon and endpoint free process.
  */
@@ -128,7 +140,7 @@ void sctp_auth_destroy_keys(struct list_head *keys)
 
 	key_for_each_safe(ep_key, tmp, keys) {
 		list_del_init(&ep_key->key_list);
-		sctp_auth_shkey_free(ep_key);
+		sctp_auth_shkey_release(ep_key);
 	}
 }
 
@@ -409,13 +421,19 @@ int sctp_auth_asoc_init_active_key(struct sctp_association *asoc, gfp_t gfp)
 
 	sctp_auth_key_put(asoc->asoc_shared_key);
 	asoc->asoc_shared_key = secret;
+	asoc->shkey = ep_key;
 
 	/* Update send queue in case any chunk already in there now
 	 * needs authenticating
 	 */
 	list_for_each_entry(chunk, &asoc->outqueue.out_chunk_list, list) {
-		if (sctp_auth_send_cid(chunk->chunk_hdr->type, asoc))
+		if (sctp_auth_send_cid(chunk->chunk_hdr->type, asoc)) {
 			chunk->auth = 1;
+			if (!chunk->shkey) {
+				chunk->shkey = asoc->shkey;
+				sctp_auth_shkey_hold(chunk->shkey);
+			}
+		}
 	}
 
 	return 0;
@@ -703,16 +721,15 @@ int sctp_auth_recv_cid(enum sctp_cid chunk, const struct sctp_association *asoc)
  *    after the AUTH chunk in the SCTP packet.
  */
 void sctp_auth_calculate_hmac(const struct sctp_association *asoc,
-			      struct sk_buff *skb,
-			      struct sctp_auth_chunk *auth,
-			      gfp_t gfp)
+			      struct sk_buff *skb, struct sctp_auth_chunk *auth,
+			      struct sctp_shared_key *ep_key, gfp_t gfp)
 {
-	struct crypto_shash *tfm;
 	struct sctp_auth_bytes *asoc_key;
+	struct crypto_shash *tfm;
 	__u16 key_id, hmac_id;
-	__u8 *digest;
 	unsigned char *end;
 	int free_key = 0;
+	__u8 *digest;
 
 	/* Extract the info we need:
 	 * - hmac id
@@ -724,12 +741,7 @@ void sctp_auth_calculate_hmac(const struct sctp_association *asoc,
 	if (key_id == asoc->active_key_id)
 		asoc_key = asoc->asoc_shared_key;
 	else {
-		struct sctp_shared_key *ep_key;
-
-		ep_key = sctp_auth_get_shkey(asoc, key_id);
-		if (!ep_key)
-			return;
-
+		/* ep_key can't be NULL here */
 		asoc_key = sctp_auth_asoc_create_secret(asoc, ep_key, gfp);
 		if (!asoc_key)
 			return;
@@ -829,7 +841,7 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
 		      struct sctp_association *asoc,
 		      struct sctp_authkey *auth_key)
 {
-	struct sctp_shared_key *cur_key = NULL;
+	struct sctp_shared_key *cur_key, *shkey;
 	struct sctp_auth_bytes *key;
 	struct list_head *sh_keys;
 	int replace = 0;
@@ -842,46 +854,34 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
 	else
 		sh_keys = &ep->endpoint_shared_keys;
 
-	key_for_each(cur_key, sh_keys) {
-		if (cur_key->key_id == auth_key->sca_keynumber) {
+	key_for_each(shkey, sh_keys) {
+		if (shkey->key_id == auth_key->sca_keynumber) {
 			replace = 1;
 			break;
 		}
 	}
 
-	/* If we are not replacing a key id, we need to allocate
-	 * a shared key.
-	 */
-	if (!replace) {
-		cur_key = sctp_auth_shkey_create(auth_key->sca_keynumber,
-						 GFP_KERNEL);
-		if (!cur_key)
-			return -ENOMEM;
-	}
+	cur_key = sctp_auth_shkey_create(auth_key->sca_keynumber, GFP_KERNEL);
+	if (!cur_key)
+		return -ENOMEM;
 
 	/* Create a new key data based on the info passed in */
 	key = sctp_auth_create_key(auth_key->sca_keylength, GFP_KERNEL);
-	if (!key)
-		goto nomem;
+	if (!key) {
+		kfree(cur_key);
+		return -ENOMEM;
+	}
 
 	memcpy(key->data, &auth_key->sca_key[0], auth_key->sca_keylength);
+	cur_key->key = key;
 
-	/* If we are replacing, remove the old keys data from the
-	 * key id.  If we are adding new key id, add it to the
-	 * list.
-	 */
-	if (replace)
-		sctp_auth_key_put(cur_key->key);
-	else
-		list_add(&cur_key->key_list, sh_keys);
+	if (replace) {
+		list_del_init(&shkey->key_list);
+		sctp_auth_shkey_release(shkey);
+	}
+	list_add(&cur_key->key_list, sh_keys);
 
-	cur_key->key = key;
 	return 0;
-nomem:
-	if (!replace)
-		sctp_auth_shkey_free(cur_key);
-
-	return -ENOMEM;
 }
 
 int sctp_auth_set_active_key(struct sctp_endpoint *ep,
@@ -952,7 +952,7 @@ int sctp_auth_del_key_id(struct sctp_endpoint *ep,
 
 	/* Delete the shared key */
 	list_del_init(&key->key_list);
-	sctp_auth_shkey_free(key);
+	sctp_auth_shkey_release(key);
 
 	return 0;
 }

net/sctp/chunk.c

@@ -168,6 +168,7 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
 {
 	size_t len, first_len, max_data, remaining;
 	size_t msg_len = iov_iter_count(from);
+	struct sctp_shared_key *shkey = NULL;
 	struct list_head *pos, *temp;
 	struct sctp_chunk *chunk;
 	struct sctp_datamsg *msg;
@@ -204,6 +205,8 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
 		if (hmac_desc)
 			max_data -= SCTP_PAD4(sizeof(struct sctp_auth_chunk) +
 					      hmac_desc->hmac_len);
+
+		shkey = asoc->shkey;
 	}
 
 	/* Check what's our max considering the above */
@@ -275,6 +278,8 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
 		if (err < 0)
 			goto errout_chunk_free;
 
+		chunk->shkey = shkey;
+
 		/* Put the chunk->skb back into the form expected by send.  */
 		__skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr -
 				       chunk->skb->data);

net/sctp/output.c

@@ -241,10 +241,13 @@ static enum sctp_xmit sctp_packet_bundle_auth(struct sctp_packet *pkt,
 	if (!chunk->auth)
 		return retval;
 
-	auth = sctp_make_auth(asoc);
+	auth = sctp_make_auth(asoc, chunk->shkey->key_id);
 	if (!auth)
 		return retval;
 
+	auth->shkey = chunk->shkey;
+	sctp_auth_shkey_hold(auth->shkey);
+
 	retval = __sctp_packet_append_chunk(pkt, auth);
 
 	if (retval != SCTP_XMIT_OK)
@@ -490,7 +493,8 @@ static int sctp_packet_pack(struct sctp_packet *packet,
 		}
 
 		if (auth) {
-			sctp_auth_calculate_hmac(tp->asoc, nskb, auth, gfp);
+			sctp_auth_calculate_hmac(tp->asoc, nskb, auth,
+						 packet->auth->shkey, gfp);
 			/* free auth if no more chunks, or add it back */
 			if (list_empty(&packet->chunk_list))
 				sctp_chunk_free(packet->auth);
@@ -770,6 +774,16 @@ static enum sctp_xmit sctp_packet_will_fit(struct sctp_packet *packet,
 	enum sctp_xmit retval = SCTP_XMIT_OK;
 	size_t psize, pmtu, maxsize;
 
+	/* Don't bundle in this packet if this chunk's auth key doesn't
+	 * match other chunks already enqueued on this packet. Also,
+	 * don't bundle the chunk with auth key if other chunks in this
+	 * packet don't have auth key.
+	 */
+	if ((packet->auth && chunk->shkey != packet->auth->shkey) ||
+	    (!packet->auth && chunk->shkey &&
+	     chunk->chunk_hdr->type != SCTP_CID_AUTH))
+		return SCTP_XMIT_PMTU_FULL;
+
 	psize = packet->size;
 	if (packet->transport->asoc)
 		pmtu = packet->transport->asoc->pathmtu;

net/sctp/sm_make_chunk.c

@@ -87,7 +87,10 @@ static void  *sctp_addto_chunk_fixed(struct sctp_chunk *, int len,
 /* Control chunk destructor */
 static void sctp_control_release_owner(struct sk_buff *skb)
 {
-	/*TODO: do memory release */
+	struct sctp_chunk *chunk = skb_shinfo(skb)->destructor_arg;
+
+	if (chunk->shkey)
+		sctp_auth_shkey_release(chunk->shkey);
 }
 
 static void sctp_control_set_owner_w(struct sctp_chunk *chunk)
@@ -102,7 +105,12 @@ static void sctp_control_set_owner_w(struct sctp_chunk *chunk)
 	 *
 	 *  For now don't do anything for now.
 	 */
+	if (chunk->auth) {
+		chunk->shkey = asoc->shkey;
+		sctp_auth_shkey_hold(chunk->shkey);
+	}
 	skb->sk = asoc ? asoc->base.sk : NULL;
+	skb_shinfo(skb)->destructor_arg = chunk;
 	skb->destructor = sctp_control_release_owner;
 }
 
@@ -1271,7 +1279,8 @@ struct sctp_chunk *sctp_make_op_error(const struct sctp_association *asoc,
 	return retval;
 }
 
-struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc)
+struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc,
+				  __u16 key_id)
 {
 	struct sctp_authhdr auth_hdr;
 	struct sctp_hmac *hmac_desc;
@@ -1289,7 +1298,7 @@ struct sctp_chunk *sctp_make_auth(const struct sctp_association *asoc)
 		return NULL;
 
 	auth_hdr.hmac_id = htons(hmac_desc->hmac_id);
-	auth_hdr.shkey_id = htons(asoc->active_key_id);
+	auth_hdr.shkey_id = htons(key_id);
 
 	retval->subh.auth_hdr = sctp_addto_chunk(retval, sizeof(auth_hdr),
 						 &auth_hdr);

net/sctp/sm_statefuns.c

@@ -4114,6 +4114,7 @@ static enum sctp_ierror sctp_sf_authenticate(
 					const union sctp_subtype type,
 					struct sctp_chunk *chunk)
 {
+	struct sctp_shared_key *sh_key = NULL;
 	struct sctp_authhdr *auth_hdr;
 	__u8 *save_digest, *digest;
 	struct sctp_hmac *hmac;
@@ -4135,9 +4136,11 @@ static enum sctp_ierror sctp_sf_authenticate(
 	 * configured
 	 */
 	key_id = ntohs(auth_hdr->shkey_id);
-	if (key_id != asoc->active_key_id && !sctp_auth_get_shkey(asoc, key_id))
-		return SCTP_IERROR_AUTH_BAD_KEYID;
-
+	if (key_id != asoc->active_key_id) {
+		sh_key = sctp_auth_get_shkey(asoc, key_id);
+		if (!sh_key)
+			return SCTP_IERROR_AUTH_BAD_KEYID;
+	}
 
 	/* Make sure that the length of the signature matches what
 	 * we expect.
@@ -4166,7 +4169,7 @@ static enum sctp_ierror sctp_sf_authenticate(
 
 	sctp_auth_calculate_hmac(asoc, chunk->skb,
 				 (struct sctp_auth_chunk *)chunk->chunk_hdr,
-				 GFP_ATOMIC);
+				 sh_key, GFP_ATOMIC);
 
 	/* Discard the packet if the digests do not match */
 	if (memcmp(save_digest, digest, sig_len)) {

net/sctp/socket.c

@@ -156,6 +156,9 @@ static inline void sctp_set_owner_w(struct sctp_chunk *chunk)
 	/* The sndbuf space is tracked per association.  */
 	sctp_association_hold(asoc);
 
+	if (chunk->shkey)
+		sctp_auth_shkey_hold(chunk->shkey);
+
 	skb_set_owner_w(chunk->skb, sk);
 
 	chunk->skb->destructor = sctp_wfree;
@@ -8109,6 +8112,9 @@ static void sctp_wfree(struct sk_buff *skb)
 	sk->sk_wmem_queued   -= skb->truesize;
 	sk_mem_uncharge(sk, skb->truesize);
 
+	if (chunk->shkey)
+		sctp_auth_shkey_release(chunk->shkey);
+
 	sock_wfree(skb);
 	sctp_wake_up_waiters(sk, asoc);