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_subr.c b/net/x25/x25_subr.c
index 24a342e..5170d52 100644
--- a/net/x25/x25_subr.c
+++ b/net/x25/x25_subr.c
@@ -269,7 +269,11 @@
int *d, int *m)
{
struct x25_sock *x25 = x25_sk(sk);
- unsigned char *frame = skb->data;
+ unsigned char *frame;
+
+ if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+ return X25_ILLEGAL;
+ frame = skb->data;
*ns = *nr = *q = *d = *m = 0;
@@ -294,6 +298,10 @@
if (frame[2] == X25_RR ||
frame[2] == X25_RNR ||
frame[2] == X25_REJ) {
+ if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
+ return X25_ILLEGAL;
+ frame = skb->data;
+
*nr = (frame[3] >> 1) & 0x7F;
return frame[2];
}
@@ -308,6 +316,10 @@
if (x25->neighbour->extended) {
if ((frame[2] & 0x01) == X25_DATA) {
+ if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
+ return X25_ILLEGAL;
+ frame = skb->data;
+
*q = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
*d = (frame[0] & X25_D_BIT) == X25_D_BIT;
*m = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;