[PATCH AUTOSEL 6.18] xfrm_user: fix info leak in build_mapping()

[Sasha Levin]

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

[ 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@xxxxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Simon Horman <horms@xxxxxxxxxx>
Assisted-by: gregkh_clanker_t1000
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---

LLM Generated explanations, may be completely bogus:

Error: Failed to generate final synthesis

 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 1ddcf2a1eff7a..b3f69c0760d4c 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -4164,6 +4164,7 @@ 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;
-- 
2.53.0