netdev - [PATCH net 3/4] ipvs: prevent integer overflow in do_ip_vs_get

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Message-Id: <20250313095636.2186-4-pablo@netfilter.org>
Date: Thu, 13 Mar 2025 10:56:35 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	fw@...len.de,
	horms@...nel.org
Subject: [PATCH net 3/4] ipvs: prevent integer overflow in do_ip_vs_get_ctl()

From: Dan Carpenter <dan.carpenter@...aro.org>

The get->num_services variable is an unsigned int which is controlled by
the user.  The struct_size() function ensures that the size calculation
does not overflow an unsigned long, however, we are saving the result to
an int so the calculation can overflow.

Both "len" and "get->num_services" come from the user.  This check is
just a sanity check to help the user and ensure they are using the API
correctly.  An integer overflow here is not a big deal.  This has no
security impact.

Save the result from struct_size() type size_t to fix this integer
overflow bug.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
Acked-by: Julian Anastasov <ja@....bg>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 7d13110ce188..0633276d96bf 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -3091,12 +3091,12 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
 	case IP_VS_SO_GET_SERVICES:
 	{
 		struct ip_vs_get_services *get;
-		int size;
+		size_t size;
 
 		get = (struct ip_vs_get_services *)arg;
 		size = struct_size(get, entrytable, get->num_services);
 		if (*len != size) {
-			pr_err("length: %u != %u\n", *len, size);
+			pr_err("length: %u != %zu\n", *len, size);
 			ret = -EINVAL;
 			goto out;
 		}
@@ -3132,12 +3132,12 @@ do_ip_vs_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
 	case IP_VS_SO_GET_DESTS:
 	{
 		struct ip_vs_get_dests *get;
-		int size;
+		size_t size;
 
 		get = (struct ip_vs_get_dests *)arg;
 		size = struct_size(get, entrytable, get->num_dests);
 		if (*len != size) {
-			pr_err("length: %u != %u\n", *len, size);
+			pr_err("length: %u != %zu\n", *len, size);
 			ret = -EINVAL;
 			goto out;
 		}
-- 
2.30.2