[patch 14/37] DCCP: Fix exploitable hole in DCCP socket options

[Greg KH <gregkh@suse.de>]

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-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

[DCCP] getsockopt: Fix DCCP_SOCKOPT_[SEND,RECV]_CSCOV

We were only checking if there was enough space to put the int, but
left len as specified by the (malicious) user, sigh, fix it by setting
len to sizeof(val) and transfering just one int worth of data, the one
asked for.

Also check for negative len values.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 net/dccp/proto.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -575,7 +575,7 @@ static int do_dccp_getsockopt(struct soc
 	if (get_user(len, optlen))
 		return -EFAULT;
 
-	if (len < sizeof(int))
+	if (len < (int)sizeof(int))
 		return -EINVAL;
 
 	dp = dccp_sk(sk);
@@ -589,9 +589,11 @@ static int do_dccp_getsockopt(struct soc
 					       (__be32 __user *)optval, optlen);
 	case DCCP_SOCKOPT_SEND_CSCOV:
 		val = dp->dccps_pcslen;
+		len = sizeof(val);
 		break;
 	case DCCP_SOCKOPT_RECV_CSCOV:
 		val = dp->dccps_pcrlen;
+		len = sizeof(val);
 		break;
 	case 128 ... 191:
 		return ccid_hc_rx_getsockopt(dp->dccps_hc_rx_ccid, sk, optname,

--