From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Jeremy Kerr <jk@codeconstruct.com.au>,
	Simon Horman <horms@kernel.org>,
	Jakub Kicinski <kuba@kernel.org>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.19 635/781] net: mctp: ensure our nlmsg responses are initialised
Date: Tue, 24 Feb 2026 17:22:24 -0800
Message-ID: <20260225012415.382185816@linuxfoundation.org>
In-Reply-To: <20260225012359.695468795@linuxfoundation.org>
References: <20260225012359.695468795@linuxfoundation.org>
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6.19-stable review patch.  If anyone has any objections, please let me know.

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

From: Jeremy Kerr <jk@codeconstruct.com.au>

[ Upstream commit a6a9bc544b675d8b5180f2718ec985ad267b5cbf ]

Syed Faraz Abrar (@farazsth98) from Zellic, and Pumpkin (@u1f383) from
DEVCORE Research Team working with Trend Micro Zero Day Initiative
report that a RTM_GETNEIGH will return uninitalised data in the pad
bytes of the ndmsg data.

Ensure we're initialising the netlink data to zero, in the link, addr
and neigh response messages.

Fixes: 831119f88781 ("mctp: Add neighbour netlink interface")
Fixes: 06d2f4c583a7 ("mctp: Add netlink route management")
Fixes: 583be982d934 ("mctp: Add device handling and netlink interface")
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260209-dev-mctp-nlmsg-v1-1-f1e30c346a43@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/mctp/device.c | 1 +
 net/mctp/neigh.c  | 1 +
 net/mctp/route.c  | 1 +
 3 files changed, 3 insertions(+)

diff --git a/net/mctp/device.c b/net/mctp/device.c
index 4d404edd7446e..04c5570bacff6 100644
--- a/net/mctp/device.c
+++ b/net/mctp/device.c
@@ -70,6 +70,7 @@ static int mctp_fill_addrinfo(struct sk_buff *skb,
 		return -EMSGSIZE;
 
 	hdr = nlmsg_data(nlh);
+	memset(hdr, 0, sizeof(*hdr));
 	hdr->ifa_family = AF_MCTP;
 	hdr->ifa_prefixlen = 0;
 	hdr->ifa_flags = 0;
diff --git a/net/mctp/neigh.c b/net/mctp/neigh.c
index 05b899f22d902..fc85f0e693014 100644
--- a/net/mctp/neigh.c
+++ b/net/mctp/neigh.c
@@ -218,6 +218,7 @@ static int mctp_fill_neigh(struct sk_buff *skb, u32 portid, u32 seq, int event,
 		return -EMSGSIZE;
 
 	hdr = nlmsg_data(nlh);
+	memset(hdr, 0, sizeof(*hdr));
 	hdr->ndm_family = AF_MCTP;
 	hdr->ndm_ifindex = dev->ifindex;
 	hdr->ndm_state = 0; // TODO other state bits?
diff --git a/net/mctp/route.c b/net/mctp/route.c
index 2ac4011a953ff..ecbbe4beb2133 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -1643,6 +1643,7 @@ static int mctp_fill_rtinfo(struct sk_buff *skb, struct mctp_route *rt,
 		return -EMSGSIZE;
 
 	hdr = nlmsg_data(nlh);
+	memset(hdr, 0, sizeof(*hdr));
 	hdr->rtm_family = AF_MCTP;
 
 	/* we use the _len fields as a number of EIDs, rather than
-- 
2.51.0