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Wythe" To: pablo@netfilter.org, kadlec@netfilter.org, fw@strlen.de Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, coreteam@netfilter.org, netfilter-devel@vger.kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, ast@kernel.org Subject: [RFC nf-next v4 1/2] netfilter: bpf: support prog update Date: Fri, 29 Dec 2023 15:54:08 +0800 Message-Id: <1703836449-88705-2-git-send-email-alibuda@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1703836449-88705-1-git-send-email-alibuda@linux.alibaba.com> References: <1703836449-88705-1-git-send-email-alibuda@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: From: "D. Wythe" 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 --- net/netfilter/nf_bpf_link.c | 50 ++++++++++++++++++++++++++++++--------------- 1 file changed, 34 insertions(+), 16 deletions(-) diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c index e502ec0..7c32ccb 100644 --- a/net/netfilter/nf_bpf_link.c +++ b/net/netfilter/nf_bpf_link.c @@ -8,26 +8,26 @@ #include #include -static unsigned int nf_hook_run_bpf(void *bpf_prog, struct sk_buff *skb, - const struct nf_hook_state *s) -{ - const struct bpf_prog *prog = bpf_prog; - struct bpf_nf_ctx ctx = { - .state = s, - .skb = skb, - }; - - return bpf_prog_run(prog, &ctx); -} - struct bpf_nf_link { struct bpf_link link; struct nf_hook_ops hook_ops; 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_raw(nf_link->link.prog), &ctx); +} + #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, @@ -126,8 +126,7 @@ static void bpf_nf_link_release(struct bpf_link *link) static void bpf_nf_link_dealloc(struct bpf_link *link) { struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link); - - kfree(nf_link); + kfree_rcu(nf_link, head); } static int bpf_nf_link_detach(struct bpf_link *link) @@ -162,7 +161,22 @@ static int bpf_nf_link_fill_link_info(const struct bpf_link *link, static int bpf_nf_link_update(struct bpf_link *link, struct bpf_prog *new_prog, struct bpf_prog *old_prog) { - return -EOPNOTSUPP; + struct bpf_nf_link *nf_link = container_of(link, struct bpf_nf_link, link); + int err = 0; + + if (nf_link->dead) + return -EPERM; + + if (old_prog) { + /* target old_prog mismatch */ + if (!cmpxchg(&link->prog, old_prog, new_prog)) + return -EPERM; + } else { + old_prog = xchg(&link->prog, new_prog); + } + + bpf_prog_put(old_prog); + return err; } static const struct bpf_link_ops bpf_nf_link_lops = { @@ -226,7 +240,11 @@ int bpf_nf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) link->hook_ops.hook = nf_hook_run_bpf; link->hook_ops.hook_ops_type = NF_HOOK_OP_BPF; - link->hook_ops.priv = prog; + + /* bpf_nf_link_release & bpf_nf_link_dealloc() can ensures that link remains + * valid at all times within nf_hook_run_bpf(). + */ + link->hook_ops.priv = link; link->hook_ops.pf = attr->link_create.netfilter.pf; link->hook_ops.priority = attr->link_create.netfilter.priority; -- 1.8.3.1