[PATCH 5.15.y] xfrm: clear trailing padding in build_polexpire()

[Sasha Levin <sashal@kernel.org>]

From: Yasuaki Torimaru <yasuakitorimaru@gmail.com>

[ Upstream commit 71a98248c63c535eaa4d4c22f099b68d902006d0 ]

build_expire() clears the trailing padding bytes of struct
xfrm_user_expire after setting the hard field via memset_after(),
but the analogous function build_polexpire() does not do this for
struct xfrm_user_polexpire.

The padding bytes after the __u8 hard field are left
uninitialized from the heap allocation, and are then sent to
userspace via netlink multicast to XFRMNLGRP_EXPIRE listeners,
leaking kernel heap memory contents.

Add the missing memset_after() call, matching build_expire().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Yasuaki Torimaru <yasuakitorimaru@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
[ replaced `memset_after()` macro with equivalent manual `memset()` call ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/xfrm/xfrm_user.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index d9238e17ab427..58c61efe1d7b3 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -3389,6 +3389,8 @@ static int build_polexpire(struct sk_buff *skb, struct xfrm_policy *xp,
 		return err;
 	}
 	upe->hard = !!hard;
+	/* clear the padding bytes */
+	memset(&upe->hard + 1, 0, sizeof(*upe) - offsetofend(typeof(*upe), hard));
 
 	nlmsg_end(skb, nlh);
 	return 0;
-- 
2.53.0