From patchwork Wed May 17 05:22:32 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Fastabend X-Patchwork-Id: 13244210 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 1788F538D; Wed, 17 May 2023 05:23:01 +0000 (UTC) Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2720C40D1; Tue, 16 May 2023 22:22:51 -0700 (PDT) Received: by mail-pj1-x1031.google.com with SMTP id 98e67ed59e1d1-24e14a24c9dso383282a91.0; Tue, 16 May 2023 22:22:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1684300970; x=1686892970; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=huaGQx94IhqjlpBZz9Dh/6dEAcqnZNQFnDotU/ZG3V0=; b=cvypauWx5vBeQkgQvwh0r3V+rU0e6RtAJ5zv+CimzVDoWsgBNFREY/UU+CR8ehDOky zbWE1S/QEjDpdZyhJOvd54v0K3fJQvQCwcMEZb32qOAg4vGscIbdORuNCZp7b0ncwuY6 /7qUbz+Jb01S6FLeqLnjRlmFwB7zIY3uy7frKm04OGaorzVJMZBHzoi+JSajzPaGOpkl Gz5VyjIL6lIM9RIRsGvlAQfEVWdk2/1cqU6WJQ/vn1yY6J9fmr8xDpfWEhh1gD967wYQ iUTBzu/gr3t/SzZdIfumwjq7RGcGLXjBNygpDgctsqpSrYqcGM/07Zqd3gaqUNZcJNC4 1zhA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684300970; x=1686892970; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=huaGQx94IhqjlpBZz9Dh/6dEAcqnZNQFnDotU/ZG3V0=; b=KYseAo6j90qIasKCqEVt08a8Y3xSYQidt9Aa9EXlt7KexS01jTHAVhVTUXcwxhfV7v z/AF7OKp/5gzy/ZJHwLQLbLGe0/rgj+U7aiZGNwqqsteYrNC2tAzATP+6thkNhGQKZRX Js51YO4tyL+SZ6AqJbqFUamYD78vNpH7sIRTuaLbGyRC9QxHPOWhByaDkOrDuykv0aww SGLRGOeQdGIRy8JIoGqFILeF4PfRtLkEqNasXa2Ee2urUR6x82o0YFaRg6TwzpnYjwWi zYWlLpBYla5Jj0qvBrA8O3/15s6KoCv07pjP74G1JeOgaClviLOgdMbJTUt74SwLs2sf DXEg== X-Gm-Message-State: AC+VfDw5worJNG2lbNPHdn4Z9wygCdG0+rm9V1UdmnMbQJxE9AT90gB7 iNO0lonhwTn39pdzUzG0O5s= X-Google-Smtp-Source: ACHHUZ7SVh07as+YfXygj+qui8XOZsLSUD7puZyrJbMRRgwAZXCZQFl1Mb9au8kji+d9H8STG4heVw== X-Received: by 2002:a17:90b:807:b0:252:f526:c0c5 with SMTP id bk7-20020a17090b080700b00252f526c0c5mr9895232pjb.43.1684300970443; Tue, 16 May 2023 22:22:50 -0700 (PDT) Received: from john.lan ([98.97.37.198]) by smtp.gmail.com with ESMTPSA id n11-20020a17090a2fcb00b0023cfdbb6496sm581779pjm.1.2023.05.16.22.22.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 May 2023 22:22:50 -0700 (PDT) From: John Fastabend To: jakub@cloudflare.com, daniel@iogearbox.net Cc: john.fastabend@gmail.com, bpf@vger.kernel.org, netdev@vger.kernel.org, edumazet@google.com, ast@kernel.org, andrii@kernel.org, will@isovalent.com Subject: [PATCH bpf v8 01/13] bpf: sockmap, pass skb ownership through read_skb Date: Tue, 16 May 2023 22:22:32 -0700 Message-Id: <20230517052244.294755-2-john.fastabend@gmail.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20230517052244.294755-1-john.fastabend@gmail.com> References: <20230517052244.294755-1-john.fastabend@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net The read_skb hook calls consume_skb() now, but this means that if the recv_actor program wants to use the skb it needs to inc the ref cnt so that the consume_skb() doesn't kfree the sk_buff. This is problematic because in some error cases under memory pressure we may need to linearize the sk_buff from sk_psock_skb_ingress_enqueue(). Then we get this, skb_linearize() __pskb_pull_tail() pskb_expand_head() BUG_ON(skb_shared(skb)) Because we incremented users refcnt from sk_psock_verdict_recv() we hit the bug on with refcnt > 1 and trip it. To fix lets simply pass ownership of the sk_buff through the skb_read call. Then we can drop the consume from read_skb handlers and assume the verdict recv does any required kfree. Bug found while testing in our CI which runs in VMs that hit memory constraints rather regularly. William tested TCP read_skb handlers. [ 106.536188] ------------[ cut here ]------------ [ 106.536197] kernel BUG at net/core/skbuff.c:1693! [ 106.536479] invalid opcode: 0000 [#1] PREEMPT SMP PTI [ 106.536726] CPU: 3 PID: 1495 Comm: curl Not tainted 5.19.0-rc5 #1 [ 106.537023] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ArchLinux 1.16.0-1 04/01/2014 [ 106.537467] RIP: 0010:pskb_expand_head+0x269/0x330 [ 106.538585] RSP: 0018:ffffc90000138b68 EFLAGS: 00010202 [ 106.538839] RAX: 000000000000003f RBX: ffff8881048940e8 RCX: 0000000000000a20 [ 106.539186] RDX: 0000000000000002 RSI: 0000000000000000 RDI: ffff8881048940e8 [ 106.539529] RBP: ffffc90000138be8 R08: 00000000e161fd1a R09: 0000000000000000 [ 106.539877] R10: 0000000000000018 R11: 0000000000000000 R12: ffff8881048940e8 [ 106.540222] R13: 0000000000000003 R14: 0000000000000000 R15: ffff8881048940e8 [ 106.540568] FS: 00007f277dde9f00(0000) GS:ffff88813bd80000(0000) knlGS:0000000000000000 [ 106.540954] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 106.541227] CR2: 00007f277eeede64 CR3: 000000000ad3e000 CR4: 00000000000006e0 [ 106.541569] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 106.541915] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 106.542255] Call Trace: [ 106.542383] [ 106.542487] __pskb_pull_tail+0x4b/0x3e0 [ 106.542681] skb_ensure_writable+0x85/0xa0 [ 106.542882] sk_skb_pull_data+0x18/0x20 [ 106.543084] bpf_prog_b517a65a242018b0_bpf_skskb_http_verdict+0x3a9/0x4aa9 [ 106.543536] ? migrate_disable+0x66/0x80 [ 106.543871] sk_psock_verdict_recv+0xe2/0x310 [ 106.544258] ? sk_psock_write_space+0x1f0/0x1f0 [ 106.544561] tcp_read_skb+0x7b/0x120 [ 106.544740] tcp_data_queue+0x904/0xee0 [ 106.544931] tcp_rcv_established+0x212/0x7c0 [ 106.545142] tcp_v4_do_rcv+0x174/0x2a0 [ 106.545326] tcp_v4_rcv+0xe70/0xf60 [ 106.545500] ip_protocol_deliver_rcu+0x48/0x290 [ 106.545744] ip_local_deliver_finish+0xa7/0x150 Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()") Reported-by: William Findlay Tested-by: William Findlay Reviewed-by: Jakub Sitnicki Signed-off-by: John Fastabend --- net/core/skmsg.c | 2 -- net/ipv4/tcp.c | 1 - net/ipv4/udp.c | 7 ++----- net/unix/af_unix.c | 7 ++----- 4 files changed, 4 insertions(+), 13 deletions(-) diff --git a/net/core/skmsg.c b/net/core/skmsg.c index f81883759d38..4a3dc8d27295 100644 --- a/net/core/skmsg.c +++ b/net/core/skmsg.c @@ -1183,8 +1183,6 @@ static int sk_psock_verdict_recv(struct sock *sk, struct sk_buff *skb) int ret = __SK_DROP; int len = skb->len; - skb_get(skb); - rcu_read_lock(); psock = sk_psock(sk); if (unlikely(!psock)) { diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 288693981b00..1be305e3d3c7 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1770,7 +1770,6 @@ int tcp_read_skb(struct sock *sk, skb_read_actor_t recv_actor) WARN_ON_ONCE(!skb_set_owner_sk_safe(skb, sk)); tcp_flags = TCP_SKB_CB(skb)->tcp_flags; used = recv_actor(sk, skb); - consume_skb(skb); if (used < 0) { if (!copied) copied = used; diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index c605d171eb2d..8aaae82e78ae 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1813,7 +1813,7 @@ EXPORT_SYMBOL(__skb_recv_udp); int udp_read_skb(struct sock *sk, skb_read_actor_t recv_actor) { struct sk_buff *skb; - int err, copied; + int err; try_again: skb = skb_recv_udp(sk, MSG_DONTWAIT, &err); @@ -1832,10 +1832,7 @@ int udp_read_skb(struct sock *sk, skb_read_actor_t recv_actor) } WARN_ON_ONCE(!skb_set_owner_sk_safe(skb, sk)); - copied = recv_actor(sk, skb); - kfree_skb(skb); - - return copied; + return recv_actor(sk, skb); } EXPORT_SYMBOL(udp_read_skb); diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 0b0f18ecce44..bb34852bf947 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -2553,7 +2553,7 @@ static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor) { struct unix_sock *u = unix_sk(sk); struct sk_buff *skb; - int err, copied; + int err; mutex_lock(&u->iolock); skb = skb_recv_datagram(sk, MSG_DONTWAIT, &err); @@ -2561,10 +2561,7 @@ static int unix_read_skb(struct sock *sk, skb_read_actor_t recv_actor) if (!skb) return err; - copied = recv_actor(sk, skb); - kfree_skb(skb); - - return copied; + return recv_actor(sk, skb); } /*