From c2779ae9a3e5a044e5ccd564681511bbbcc5fc0f Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Mon, 6 Apr 2026 17:33:03 +0200
Subject: [PATCH] xfrm_user: fix info leak in build_mapping()

[ Upstream commit 1beb76b2053b68c491b78370794b8ff63c8f8c02 ]

struct xfrm_usersa_id has a one-byte padding hole after the proto
field, which ends up never getting set to zero before copying out to
userspace.  Fix that up by zeroing out the whole structure before
setting individual variables.

Fixes: 3a2dfbe8acb1 ("xfrm: Notify changes in UDP encapsulation via netlink")
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Assisted-by: gregkh_clanker_t1000
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/xfrm/xfrm_user.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index dcf433894951..7e09ab9c34af 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -3592,6 +3592,7 @@ static int build_mapping(struct sk_buff *skb, struct xfrm_state *x,
 
 	um = nlmsg_data(nlh);
 
+	memset(&um->id, 0, sizeof(um->id));
 	memcpy(&um->id.daddr, &x->id.daddr, sizeof(um->id.daddr));
 	um->id.spi = x->id.spi;
 	um->id.family = x->props.family;