netdev - [PATCH net 5/6] netfilter: ipset: Hold module reference while requesting a module

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Message-Id: <20241205002854.162490-6-pablo@netfilter.org>
Date: Thu,  5 Dec 2024 01:28:53 +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
Subject: [PATCH net 5/6] netfilter: ipset: Hold module reference while requesting a module

From: Phil Sutter <phil@....cc>

User space may unload ip_set.ko while it is itself requesting a set type
backend module, leading to a kernel crash. The race condition may be
provoked by inserting an mdelay() right after the nfnl_unlock() call.

Fixes: a7b4f989a629 ("netfilter: ipset: IP set core support")
Signed-off-by: Phil Sutter <phil@....cc>
Acked-by: Jozsef Kadlecsik <kadlec@...filter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/ipset/ip_set_core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
index 61431690cbd5..cc20e6d56807 100644
--- a/net/netfilter/ipset/ip_set_core.c
+++ b/net/netfilter/ipset/ip_set_core.c
@@ -104,14 +104,19 @@ find_set_type(const char *name, u8 family, u8 revision)
 static bool
 load_settype(const char *name)
 {
+	if (!try_module_get(THIS_MODULE))
+		return false;
+
 	nfnl_unlock(NFNL_SUBSYS_IPSET);
 	pr_debug("try to load ip_set_%s\n", name);
 	if (request_module("ip_set_%s", name) < 0) {
 		pr_warn("Can't find ip_set type %s\n", name);
 		nfnl_lock(NFNL_SUBSYS_IPSET);
+		module_put(THIS_MODULE);
 		return false;
 	}
 	nfnl_lock(NFNL_SUBSYS_IPSET);
+	module_put(THIS_MODULE);
 	return true;
 }
 
-- 
2.30.2