x25: Handle undersized/fragmented skbs
There are multiple locations in the X.25 packet layer where a skb is
assumed to be of at least a certain size and that all its data is
currently available at skb->data. These assumptions are not checked,
hence buffer overreads may occur. Use pskb_may_pull to check these
minimal size assumptions and ensure that data is available at skb->data
when necessary, as well as use skb_copy_bits where needed.
Signed-off-by: Matthew Daley <mattjd@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Andrew Hendry <andrew.hendry@gmail.com>
Cc: stable <stable@kernel.org>
Acked-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c
index 63488fd..a49cd4e 100644
--- a/net/x25/x25_in.c
+++ b/net/x25/x25_in.c
@@ -107,6 +107,8 @@
/*
* Parse the data in the frame.
*/
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+ goto out_clear;
skb_pull(skb, X25_STD_MIN_LEN);
len = x25_parse_address_block(skb, &source_addr,
@@ -130,9 +132,8 @@
if (skb->len > X25_MAX_CUD_LEN)
goto out_clear;
- skb_copy_from_linear_data(skb,
- x25->calluserdata.cuddata,
- skb->len);
+ skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
+ skb->len);
x25->calluserdata.cudlength = skb->len;
}
if (!sock_flag(sk, SOCK_DEAD))
@@ -140,6 +141,9 @@
break;
}
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
break;
@@ -167,6 +171,9 @@
switch (frametype) {
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
@@ -180,6 +187,11 @@
}
return 0;
+
+out_clear:
+ x25_write_internal(sk, X25_CLEAR_REQUEST);
+ x25_start_t23timer(sk);
+ return 0;
}
/*
@@ -209,6 +221,9 @@
break;
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
@@ -307,6 +322,12 @@
}
return queued;
+
+out_clear:
+ x25_write_internal(sk, X25_CLEAR_REQUEST);
+ x25->state = X25_STATE_2;
+ x25_start_t23timer(sk);
+ return 0;
}
/*
@@ -316,13 +337,13 @@
*/
static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
{
+ struct x25_sock *x25 = x25_sk(sk);
+
switch (frametype) {
case X25_RESET_REQUEST:
x25_write_internal(sk, X25_RESET_CONFIRMATION);
case X25_RESET_CONFIRMATION: {
- struct x25_sock *x25 = x25_sk(sk);
-
x25_stop_timer(sk);
x25->condition = 0x00;
x25->va = 0;
@@ -334,6 +355,9 @@
break;
}
case X25_CLEAR_REQUEST:
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+ goto out_clear;
+
x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
break;
@@ -343,6 +367,12 @@
}
return 0;
+
+out_clear:
+ x25_write_internal(sk, X25_CLEAR_REQUEST);
+ x25->state = X25_STATE_2;
+ x25_start_t23timer(sk);
+ return 0;
}
/* Higher level upcall for a LAPB frame */