[PATCH] tipc: fix size validations for the MSG_CRYPTO type

From: Max VA <redacted>

The function tipc_crypto_key_rcv is used to parse MSG_CRYPTO messages
to receive keys from other nodes in the cluster in order to decrypt any
further messages from them.
This patch verifies that any supplied sizes in the message body are
valid for the received message.

Fixes: 1ef6f7c9390f ("tipc: add automatic session key exchange")
Signed-off-by: Max VA <redacted>
Acked-by: Ying Xue <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
  net/tipc/crypto.c | 32 +++++++++++++++++++++-----------
  1 file changed, 21 insertions(+), 11 deletions(-)

Max's email system doesn't seem to be able to send non-attachment
patches out, so I'm forwarding this on for him.  It's already acked by
one of the tipc maintainers.

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index c9391d38de85..dc60c32bb70d 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c

@@ -2285,43 +2285,53 @@ static bool tipc_crypto_key_rcv(struct tipc_crypto *rx, struct tipc_msg *hdr)
  	u16 key_gen = msg_key_gen(hdr);
  	u16 size = msg_data_sz(hdr);
  	u8 *data = msg_data(hdr);
+	unsigned int keylen;
+
+	/* Verify whether the size can exist in the packet */
+	if (unlikely(size < sizeof(struct tipc_aead_key) + TIPC_AEAD_KEYLEN_MIN)) {
+		pr_debug("%s: message data size is too small\n", rx->name);
+		goto exit;
+	}
+
+	keylen = ntohl(*((__be32 *)(data + TIPC_AEAD_ALG_NAME)));
+
+	/* Verify the supplied size values */
+	if (unlikely(size != keylen + sizeof(struct tipc_aead_key) ||
+		     keylen > TIPC_AEAD_KEY_SIZE_MAX)) {
+		pr_debug("%s: invalid MSG_CRYPTO key size\n", rx->name);
+		goto exit;
+	}
  
  	spin_lock(&rx->lock);
  	if (unlikely(rx->skey || (key_gen == rx->key_gen && rx->key.keys))) {
  		pr_err("%s: key existed <%p>, gen %d vs %d\n", rx->name,
  		       rx->skey, key_gen, rx->key_gen);
-		goto exit;
+		goto exit_unlock;
  	}
  
  	/* Allocate memory for the key */
  	skey = kmalloc(size, GFP_ATOMIC);
  	if (unlikely(!skey)) {
  		pr_err("%s: unable to allocate memory for skey\n", rx->name);
-		goto exit;
+		goto exit_unlock;
  	}
  
  	/* Copy key from msg data */
-	skey->keylen = ntohl(*((__be32 *)(data + TIPC_AEAD_ALG_NAME)));
+	skey->keylen = keylen;
  	memcpy(skey->alg_name, data, TIPC_AEAD_ALG_NAME);
  	memcpy(skey->key, data + TIPC_AEAD_ALG_NAME + sizeof(__be32),
  	       skey->keylen);
  
-	/* Sanity check */
-	if (unlikely(size != tipc_aead_key_size(skey))) {
-		kfree(skey);
-		skey = NULL;
-		goto exit;
-	}
-
  	rx->key_gen = key_gen;
  	rx->skey_mode = msg_key_mode(hdr);
  	rx->skey = skey;
  	rx->nokey = 0;
  	mb(); /* for nokey flag */
  
-exit:
+exit_unlock:
  	spin_unlock(&rx->lock);
  
+exit:
  	/* Schedule the key attaching on this crypto */
  	if (likely(skey && queue_delayed_work(tx->wq, &rx->work, 0)))
  		return true;