netdev - [PATCH net] net: mctp: ensure our nlmsg responses are initialised

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Message-Id: <20260209-dev-mctp-nlmsg-v1-1-f1e30c346a43@codeconstruct.com.au>
Date: Mon, 09 Feb 2026 15:27:33 +0800
From: Jeremy Kerr <jk@...econstruct.com.au>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>
Cc: Matt Johnston <matt@...econstruct.com.au>, netdev@...r.kernel.org
Subject: [PATCH net] net: mctp: ensure our nlmsg responses are initialised

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@...econstruct.com.au>
---
 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 4d404edd7446e187dd3aa18ee2086c4e2e3da3ee..04c5570bacff69690456d73490a9e4bdebf49d8d 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 05b899f22d902b275ca1e300542a8d546d59ea15..fc85f0e693014309da9c60e46485466cb5bb6dda 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 2ac4011a953fffe9e01f3bfe0f571b3727b3e903..ecbbe4beb2133b90d2a02031baaa058644f0e8fe 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

---
base-commit: 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b
change-id: 20251205-dev-mctp-nlmsg-69dbefa5df7f

Best regards,
-- 
Jeremy Kerr <jk@...econstruct.com.au>