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SubjectRe:Re: [PATCH] net/packet: fix race condition between fanout_add and __unregister_prot_hook
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On Fri, Sep 15, 2017 at 10:46 AM, Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
>
> In case of failure we also need to unlink and free match. I
> sent the following:
>
> http://patchwork.ozlabs.org/patch/813945/

+ spin_lock(&po->bind_lock);
+ if (po->running &&
+ match->type == type &&
match->prot_hook.type == po->prot_hook.type &&
match->prot_hook.dev == po->prot_hook.dev) {
err = -ENOSPC;
@@ -1761,6 +1760,13 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
err = 0;
}
}
+ spin_unlock(&po->bind_lock);
+
+ if (err && !refcount_read(&match->sk_ref)) {
+ list_del(&match->list);
+ kfree(match);
+ }


In the function fanout_add add spin_lock to protect po-> running and po-> fanout,
then whether it should be in the function fanout_release also add spin_lock protection ?

static struct packet_fanout *fanout_release(struct sock *sk)
....
mutex_lock(&fanout_mutex);
f = po->fanout;
if (f) {
po->fanout = NULL;
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