[ 066/135] dccp: fix info leak via getsockopt(DCCP_SOCKOPT_CCID_TX_INFO)

[Ben Hutchings]

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

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

From: Mathias Krause <minipli@xxxxxxxxxxxxxx>

[ Upstream commit 7b07f8eb75aa3097cdfd4f6eac3da49db787381d ]

The CCID3 code fails to initialize the trailing padding bytes of struct
tfrc_tx_info added for alignment on 64 bit architectures. It that for
potentially leaks four bytes kernel stack via the getsockopt() syscall.
Add an explicit memset(0) before filling the structure to avoid the
info leak.

Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
Cc: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/dccp/ccids/ccid3.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 3d604e1..4caf63f 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -532,6 +532,7 @@ static int ccid3_hc_tx_getsockopt(struct sock *sk, const int optname, int len,
 	case DCCP_SOCKOPT_CCID_TX_INFO:
 		if (len < sizeof(tfrc))
 			return -EINVAL;
+		memset(&tfrc, 0, sizeof(tfrc));
 		tfrc.tfrctx_x	   = hc->tx_x;
 		tfrc.tfrctx_x_recv = hc->tx_x_recv;
 		tfrc.tfrctx_x_calc = hc->tx_x_calc;


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