dccp: check ccid before dereferencing

commit 276bdb82dedb290511467a5a4fdbe9f0b52dce6f upstream.

ccid_hc_rx_getsockopt() and ccid_hc_tx_getsockopt() might be called with
a NULL ccid pointer leading to a NULL pointer dereference. This could
lead to a privilege escalation if the attacker is able to map page 0 and
prepare it with a fake ccid_ops pointer.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index 75c3582a7678ab418771b2a5ad5fd3c069a9e512..fb85d371a8dec875a01205b22ef6ddef5e99d511 100644 (file)
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -246,7 +246,7 @@ static inline int ccid_hc_rx_getsockopt(struct ccid *ccid, struct sock *sk,
                                        u32 __user *optval, int __user *optlen)
 {
        int rc = -ENOPROTOOPT;
-       if (ccid->ccid_ops->ccid_hc_rx_getsockopt != NULL)
+       if (ccid != NULL && ccid->ccid_ops->ccid_hc_rx_getsockopt != NULL)
                rc = ccid->ccid_ops->ccid_hc_rx_getsockopt(sk, optname, len,
                                                 optval, optlen);
        return rc;
@@ -257,7 +257,7 @@ static inline int ccid_hc_tx_getsockopt(struct ccid *ccid, struct sock *sk,
                                        u32 __user *optval, int __user *optlen)
 {
        int rc = -ENOPROTOOPT;
-       if (ccid->ccid_ops->ccid_hc_tx_getsockopt != NULL)
+       if (ccid != NULL && ccid->ccid_ops->ccid_hc_tx_getsockopt != NULL)
                rc = ccid->ccid_ops->ccid_hc_tx_getsockopt(sk, optname, len,
                                                 optval, optlen);
        return rc;