linux-kernel - [PATCH net] net: netlink: prevent potential integer overflow in nlmsg

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Message-ID: <58023f9e-555e-48db-9822-283c2c1f6d0e@stanley.mountain>
Date: Wed, 22 Jan 2025 16:49:17 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Thomas Graf <tgraf@...g.ch>
Cc: "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>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH net] net: netlink: prevent potential integer overflow in
 nlmsg_new()

The "payload" variable is type size_t, however the nlmsg_total_size()
function will a few bytes to it and then truncate the result to type
int.  That means that if "payload" is more than UINT_MAX the alloc_skb()
function might allocate a buffer which is smaller than intended.

Cc: stable@...r.kernel.org
Fixes: bfa83a9e03cf ("[NETLINK]: Type-safe netlink messages/attributes interface")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 include/net/netlink.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/net/netlink.h b/include/net/netlink.h
index e015ffbed819..ca7a8152e6d4 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -1015,6 +1015,8 @@ static inline struct nlmsghdr *nlmsg_put_answer(struct sk_buff *skb,
  */
 static inline struct sk_buff *nlmsg_new(size_t payload, gfp_t flags)
 {
+	if (payload > INT_MAX)
+		return NULL;
 	return alloc_skb(nlmsg_total_size(payload), flags);
 }
 
-- 
2.45.2