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authorBreno Leitao <leitao@debian.org>2024-12-02 16:22:05 -0800
committerJakub Kicinski <kuba@kernel.org>2024-12-04 18:41:37 -0800
commita9ab02ed97c654a9ea09afb3e6294cea3768c388 (patch)
tree33e3a623ee029eb2eb5db74cdda20db004c65d84
parentbb18265c3aba92b91a1355609769f3e967b65dee (diff)
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[1]. 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. Link: https://lore.kernel.org/lkml/Zz1cKZYt1e7elibV@gondor.apana.org.au/ [1] Suggested-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Breno Leitao <leitao@debian.org> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Link: https://patch.msgid.link/20241202-netpoll_rcu_herbet_fix-v2-1-2b9d58edc76a@debian.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
-rw-r--r--net/core/netpoll.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 2e459b9d88eb..99e5aa9cc992 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -634,7 +634,8 @@ 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;
@@ -654,7 +655,6 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
goto free_npinfo;
}
} else {
- npinfo = rtnl_dereference(ndev->npinfo);
refcount_inc(&npinfo->refcnt);
}