[PATCH ovpn net v2 6/9] ovpn: zero-initialize sockaddr before learning a floated endpoint

From: Antonio Quartulli <[email protected]>

ovpn_peer_endpoints_update() builds the new remote endpoint in an
on-stack struct sockaddr_storage that is left uninitialized. For IPv4
only sin_family/sin_addr/sin_port are written, leaving the 8-byte
sin_zero padding as stack garbage (for IPv6, sin6_flowinfo is left
uninitialized likewise).

ovpn_peer_reset_sockaddr() -> ovpn_bind_from_sockaddr() then memcpy()s
sizeof(struct sockaddr_in)/sizeof(struct sockaddr_in6) bytes - padding
included - into bind->remote. That buffer is later hashed with jhash()
over the same length to place the peer in the by_transp_addr table, so
the garbage padding lands the floated peer in an essentially random
bucket. Lockless lookups in ovpn_peer_get_by_transp_addr() build their
key from a zero-initialized sockaddr_storage, compute a different bucket
and fail to find the peer.

This is also a plain use of uninitialized stack memory in jhash().

Zero-initialize the sockaddr_storage, matching what the lookup and
netlink paths already do.

Fixes: f0281c1d3732 ("ovpn: add support for updating local or remote UDP endpoint")
Signed-off-by: Antonio Quartulli <[email protected]>
---
 drivers/net/ovpn/peer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c
index ee88251f2196..4aa5edc75dec 100644
--- a/drivers/net/ovpn/peer.c
+++ b/drivers/net/ovpn/peer.c
@@ -220,7 +220,7 @@ static void __ovpn_peer_hash_transp_addr(struct ovpn_peer *peer,
  */
 void ovpn_peer_endpoints_update(struct ovpn_peer *peer, struct sk_buff *skb)
 {
-	struct sockaddr_storage ss;
+	struct sockaddr_storage ss = {};
 	struct sockaddr_in6 *sa6;
 	bool reset_cache = false;
 	struct sockaddr_in *sa;
-- 
2.53.0