From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB80528DBB; Fri, 24 Nov 2023 18:51:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="jGpi6V6V" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B757C433C8; Fri, 24 Nov 2023 18:51:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700851865; bh=PsVuzbH8evEjcyOL6DCxPD3GGMLUMhVPOy6q5fbkPCg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jGpi6V6Vvf5eHA3QRXjE6dppf+BkInogzGQWbu+nxe55WotOkM748GRKM7fnC70/x RzYDClTJ7kOUG1NP4fkUGuxZcaJQPvmR7s6c+CnrdkeV2NjGMCvPnXDoPwpDNaJXZ+ tsXn0Bq4kJuyyLjkejkLmXuuzzOf0YTJMlb0euYE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , Stanislav Fomichev , Kuniyuki Iwashima , "David S. Miller" , Sasha Levin Subject: [PATCH 6.1 126/372] net: set SOCK_RCU_FREE before inserting socket into hashtable Date: Fri, 24 Nov 2023 17:48:33 +0000 Message-ID: <20231124172014.676738479@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124172010.413667921@linuxfoundation.org> References: <20231124172010.413667921@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stanislav Fomichev [ Upstream commit 871019b22d1bcc9fab2d1feba1b9a564acbb6e99 ] We've started to see the following kernel traces: WARNING: CPU: 83 PID: 0 at net/core/filter.c:6641 sk_lookup+0x1bd/0x1d0 Call Trace: __bpf_skc_lookup+0x10d/0x120 bpf_sk_lookup+0x48/0xd0 bpf_sk_lookup_tcp+0x19/0x20 bpf_prog_+0x37c/0x16a3 cls_bpf_classify+0x205/0x2e0 tcf_classify+0x92/0x160 __netif_receive_skb_core+0xe52/0xf10 __netif_receive_skb_list_core+0x96/0x2b0 napi_complete_done+0x7b5/0xb70 _poll+0x94/0xb0 net_rx_action+0x163/0x1d70 __do_softirq+0xdc/0x32e asm_call_irq_on_stack+0x12/0x20 do_softirq_own_stack+0x36/0x50 do_softirq+0x44/0x70 __inet_hash can race with lockless (rcu) readers on the other cpus: __inet_hash __sk_nulls_add_node_rcu <- (bpf triggers here) sock_set_flag(SOCK_RCU_FREE) Let's move the SOCK_RCU_FREE part up a bit, before we are inserting the socket into hashtables. Note, that the race is really harmless; the bpf callers are handling this situation (where listener socket doesn't have SOCK_RCU_FREE set) correctly, so the only annoyance is a WARN_ONCE. More details from Eric regarding SOCK_RCU_FREE timeline: Commit 3b24d854cb35 ("tcp/dccp: do not touch listener sk_refcnt under synflood") added SOCK_RCU_FREE. At that time, the precise location of sock_set_flag(sk, SOCK_RCU_FREE) did not matter, because the thread calling __inet_hash() owns a reference on sk. SOCK_RCU_FREE was only tested at dismantle time. Commit 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF") started checking SOCK_RCU_FREE _after_ the lookup to infer whether the refcount has been taken care of. Fixes: 6acc9b432e67 ("bpf: Add helper to retrieve socket in BPF") Reviewed-by: Eric Dumazet Signed-off-by: Stanislav Fomichev Reviewed-by: Kuniyuki Iwashima Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ipv4/inet_hashtables.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index 62d9472ac8bca..f2ed2aed08ab3 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -731,12 +731,12 @@ int __inet_hash(struct sock *sk, struct sock *osk) if (err) goto unlock; } + sock_set_flag(sk, SOCK_RCU_FREE); if (IS_ENABLED(CONFIG_IPV6) && sk->sk_reuseport && sk->sk_family == AF_INET6) __sk_nulls_add_node_tail_rcu(sk, &ilb2->nulls_head); else __sk_nulls_add_node_rcu(sk, &ilb2->nulls_head); - sock_set_flag(sk, SOCK_RCU_FREE); sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1); unlock: spin_unlock(&ilb2->lock); -- 2.42.0