netdev - [PATCH net] netpoll: Use rtnl_dereference() for npinfo pointer access

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20241121-netpoll_rcu_herbet_fix-v1-1-457c5fee9dfd@debian.org>
Date: Thu, 21 Nov 2024 06:58:58 -0800
From: Breno Leitao <leitao@...ian.org>
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>, 
 Michal Kubiak <michal.kubiak@...el.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kernel-team@...a.com, Herbert Xu <herbert@...dor.apana.org.au>, 
 Breno Leitao <leitao@...ian.org>
Subject: [PATCH net] netpoll: Use rtnl_dereference() for npinfo pointer
 access

In the __netpoll_setup() function, when accessing the device's npinfo
pointer, replace rcu_access_pointer() with rtnl_dereference(). This
change is more appropriate, as suggested by Herbert Xu.

The function is called with the RTNL mutex held, and the pointer is
being dereferenced later, so, dereference earlier and just reuse the
pointer for the if/else.

The replacement ensures correct pointer access while maintaining
the existing locking and RCU semantics of the netpoll subsystem.

Fixes: c75964e40e69 ("netpoll: Use rtnl_dereference() for npinfo pointer access")
Suggested-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Breno Leitao <leitao@...ian.org>
---
 net/core/netpoll.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 45fb60bc4803958eb07d4038028269fc0c19622e..30152811e0903a369ccca30500e11e696be158fd 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -626,7 +626,8 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
 		goto out;
 	}

-	if (!rcu_access_pointer(ndev->npinfo)) {
+	npinfo = rtnl_dereference(ndev->npinfo);
+	if (!npinfo) {
 		npinfo = kmalloc(sizeof(*npinfo), GFP_KERNEL);
 		if (!npinfo) {
 			err = -ENOMEM;
@@ -646,7 +647,6 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
 				goto free_npinfo;
 		}
 	} else {
-		npinfo = rtnl_dereference(ndev->npinfo);
 		refcount_inc(&npinfo->refcnt);
 	}

---
base-commit: 66418447d27b7f4c027587582a133dd0bc0a663b
change-id: 20241121-netpoll_rcu_herbet_fix-3f0a433b7860

Best regards,
-- 
Breno Leitao <leitao@...ian.org>