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    SubjectRe: [RFC nf-next v2 1/2] netfilter: bpf: support prog update
    On Mon, Dec 18, 2023 at 12:18:20PM +0800, D. Wythe wrote:
    > From: "D. Wythe" <alibuda@linux.alibaba.com>
    >
    > To support the prog update, we need to ensure that the prog seen
    > within the hook is always valid. Considering that hooks are always
    > protected by rcu_read_lock(), which provide us the ability to
    > access the prog under rcu.
    >
    > Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>

    ...

    > @@ -26,8 +17,20 @@ struct bpf_nf_link {
    > struct net *net;
    > u32 dead;
    > const struct nf_defrag_hook *defrag_hook;
    > + struct rcu_head head;
    > };
    >
    > +static unsigned int nf_hook_run_bpf(void *bpf_link, struct sk_buff *skb,
    > + const struct nf_hook_state *s)
    > +{
    > + const struct bpf_nf_link *nf_link = bpf_link;
    > + struct bpf_nf_ctx ctx = {
    > + .state = s,
    > + .skb = skb,
    > + };
    > + return bpf_prog_run(rcu_dereference(nf_link->link.prog), &ctx);

    Hi,

    AFAICT nf_link->link.prog isn't annotated as __rcu,
    so perhaps rcu_dereference() is not correct here?

    In any case, sparse seems a bit unhappy:

    .../nf_bpf_link.c:31:29: error: incompatible types in comparison expression (different address spaces):
    .../nf_bpf_link.c:31:29: struct bpf_prog [noderef] __rcu *
    .../nf_bpf_link.c:31:29: struct bpf_prog *

    > +}
    > +
    > #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) || IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
    > static const struct nf_defrag_hook *
    > get_proto_defrag_hook(struct bpf_nf_link *link,

    ...

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