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/af_x25.c b/net/x25/af_x25.c
index a4bd172..aa567b0 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -91,7 +91,7 @@
int needed;
int rc;
- if (skb->len < 1) {
+ if (!pskb_may_pull(skb, 1)) {
/* packet has no address block */
rc = 0;
goto empty;
@@ -100,7 +100,7 @@
len = *skb->data;
needed = 1 + (len >> 4) + (len & 0x0f);
- if (skb->len < needed) {
+ if (!pskb_may_pull(skb, needed)) {
/* packet is too short to hold the addresses it claims
to hold */
rc = -1;
@@ -951,10 +951,10 @@
*
* Facilities length is mandatory in call request packets
*/
- if (skb->len < 1)
+ if (!pskb_may_pull(skb, 1))
goto out_clear_request;
len = skb->data[0] + 1;
- if (skb->len < len)
+ if (!pskb_may_pull(skb, len))
goto out_clear_request;
skb_pull(skb,len);
@@ -965,6 +965,13 @@
goto out_clear_request;
/*
+ * Get all the call user data so it can be used in
+ * x25_find_listener and skb_copy_from_linear_data up ahead.
+ */
+ if (!pskb_may_pull(skb, skb->len))
+ goto out_clear_request;
+
+ /*
* Find a listener for the particular address/cud pair.
*/
sk = x25_find_listener(&source_addr,skb);
@@ -1172,6 +1179,9 @@
* byte of the user data is the logical value of the Q Bit.
*/
if (test_bit(X25_Q_BIT_FLAG, &x25->flags)) {
+ if (!pskb_may_pull(skb, 1))
+ goto out_kfree_skb;
+
qbit = skb->data[0];
skb_pull(skb, 1);
}
@@ -1250,7 +1260,9 @@
struct x25_sock *x25 = x25_sk(sk);
struct sockaddr_x25 *sx25 = (struct sockaddr_x25 *)msg->msg_name;
size_t copied;
- int qbit;
+ int qbit, header_len = x25->neighbour->extended ?
+ X25_EXT_MIN_LEN : X25_STD_MIN_LEN;
+
struct sk_buff *skb;
unsigned char *asmptr;
int rc = -ENOTCONN;
@@ -1271,6 +1283,9 @@
skb = skb_dequeue(&x25->interrupt_in_queue);
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+ goto out_free_dgram;
+
skb_pull(skb, X25_STD_MIN_LEN);
/*
@@ -1291,10 +1306,12 @@
if (!skb)
goto out;
+ if (!pskb_may_pull(skb, header_len))
+ goto out_free_dgram;
+
qbit = (skb->data[0] & X25_Q_BIT) == X25_Q_BIT;
- skb_pull(skb, x25->neighbour->extended ?
- X25_EXT_MIN_LEN : X25_STD_MIN_LEN);
+ skb_pull(skb, header_len);
if (test_bit(X25_Q_BIT_FLAG, &x25->flags)) {
asmptr = skb_push(skb, 1);