net/tls: don't copy negative amounts of data in reencrypt

[ Upstream commit 97e1caa517e22d62a283b876fb8aa5f4672c83dd ]

There is no guarantee the record starts before the skb frags.
If we don't check for this condition copy amount will get
negative, leading to reads and writes to random memory locations.
Familiar hilarity ensues.

Fixes: 4799ac81e52a ("tls: Add rx inline crypto offload")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index c9588b682db4eecd69fbcc268d40f3b76a48b334..8538ee22a5823bbc4de37ad30f4b754996233003 100644 (file)
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -600,14 +600,16 @@ static int tls_device_reencrypt(struct sock *sk, struct sk_buff *skb)
        else
                err = 0;
 
-       copy = min_t(int, skb_pagelen(skb) - offset,
-                    rxm->full_len - TLS_CIPHER_AES_GCM_128_TAG_SIZE);
+       if (skb_pagelen(skb) > offset) {
+               copy = min_t(int, skb_pagelen(skb) - offset,
+                            rxm->full_len - TLS_CIPHER_AES_GCM_128_TAG_SIZE);
 
-       if (skb->decrypted)
-               skb_store_bits(skb, offset, buf, copy);
+               if (skb->decrypted)
+                       skb_store_bits(skb, offset, buf, copy);
 
-       offset += copy;
-       buf += copy;
+               offset += copy;
+               buf += copy;
+       }
 
        skb_walk_frags(skb, skb_iter) {
                copy = min_t(int, skb_iter->len,