From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f46.google.com (mail-ot1-f46.google.com [209.85.210.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4A3E713AA2E; Thu, 22 Aug 2024 20:45:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724359556; cv=none; b=WuvMT/GURQuusj5k/Tnk6ajdmZmZAhDqbwxxGi71TDGKieo1KRuWE219xiTIO/zN+5r6rfjyYS9dQ4JXgxGNcwEwMWzW3UVP3fSpahytzxj6wW6PbrTQfDq4GuLpTnNAhFB2RGn/jrJ36Imay6cNF0ryGEbf43zNvo3gcP2MMSI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724359556; c=relaxed/simple; bh=4X4eXD1J6KuR99w3hqgsl01Ywx/0FiL8cRJGyD1iOto=; h=Date:From:To:Cc:Message-ID:In-Reply-To:References:Subject: Mime-Version:Content-Type; b=paMp6UAFeTwFc/ZFJ+urtNN6Nk9Opq3QL0HcuQcgLyJICyCLb5J4kL7HedkpeQyuPT9s6BfAtLOqhiF9hYpyC1vYd2vqi/qNG3typrN5/uDiFM3ivsmVElL5DH1HjMKxb/mTwls1LUxfYp2ScplhK9azC2w/L8xTlQCHTxqVsiI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=IuJY+LBR; arc=none smtp.client-ip=209.85.210.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IuJY+LBR" Received: by mail-ot1-f46.google.com with SMTP id 46e09a7af769-709428a9469so1071199a34.3; Thu, 22 Aug 2024 13:45:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1724359553; x=1724964353; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:subject:references :in-reply-to:message-id:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=3KalSChFzh47JfE4JuYlfPUsBnlMCnoElRFYPYzng2A=; b=IuJY+LBRhjPfy7zc0njrclPx2pWlHZBqANV8mDLDw8RAt7LWQJQYTvzISUh2i+zJ/u BZEyre7q1FM6V7xcng7hFOG7Dzlp1BaZVXjE/qljOCfRGeE07mmCqH+mz+8mS8+QXVhP z7TkKXZAJocdAZZuPBlrgdlj5r0+Qe3rhxlFmhrxDvj51MB9vKmhd36QQuOU271z4CwA NPSxbIzNwtdy8OsA0BeaQ174IywBRPsmXdIUeOlK7L9txQeTf4evo0H8QJtD5uMSZ/a8 YMEB1eKMs9D65qwNtTPM30Fxac/SUY6y1PybiE1X+bJb9SncPyeeDKqMZkwIC+0pJ96L KFfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1724359553; x=1724964353; h=content-transfer-encoding:mime-version:subject:references :in-reply-to:message-id:cc:to:from:date:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=3KalSChFzh47JfE4JuYlfPUsBnlMCnoElRFYPYzng2A=; b=Er2rS6n/2i0SL8BJlw+VfX1qCBAQAs8bkZ8vgu7o2UaAxbia6sStitqN9ZFXWEZ+lb /Mu7tayQ+S0lmyO1xUKBM09hEX1SMrgihu7VEIzvj0J4e+mIoCXXwra7fXxD8SDj5viy wN3G+EqY55ShCgvj3jFgVvmkEd/C2UovubI2+dZICAV6+JLTTNsEMjC81hvXoMZidrYw 5mTjTk+/MaPDtc6zAbnpxBWFxLxOpscWZ3t5pqMc6fAAsNyNwZV1s71unz/+A/mq1G7C VzQTrFn+0tfi1F8dH3b4vpEmy3S7mlNewBcz8yY7yUKLuGQdjUPZoQ1VQx8oLhCJyrhw 42cg== X-Forwarded-Encrypted: i=1; AJvYcCWdE/XQOfMXM9/OhGZuaxqM6Vcu3Mlzh4FB7Vk5mDZNtQYLaAb8XhdK5V15HvrVH4AFvuE=@vger.kernel.org X-Gm-Message-State: AOJu0Yx063rVbIk3jsRApmyYTUJr5wh60zX3aDDYsmbLBD/Y3SEGhDiG oX7YHnjvpNR5IotG5xXnmFeWswWuUmm3iNFu10g8uW5+CW5gLfMd X-Google-Smtp-Source: AGHT+IEWUVdkYJ0EQvahLyXPTA9UN2T2iNqB7mW6aA1xfXsnhpC7Ic/1nteElNRMMtuaS5SSe96EYg== X-Received: by 2002:a05:6808:1990:b0:3d9:b33e:d3ef with SMTP id 5614622812f47-3de2a87135emr82165b6e.3.1724359553318; Thu, 22 Aug 2024 13:45:53 -0700 (PDT) Received: from localhost ([98.97.38.69]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-7cd9ad55fe9sm1760015a12.60.2024.08.22.13.45.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Aug 2024 13:45:52 -0700 (PDT) Date: Thu, 22 Aug 2024 13:45:51 -0700 From: John Fastabend To: Cong Wang , Simon Horman Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, Cong Wang , syzbot+58c03971700330ce14d8@syzkaller.appspotmail.com, John Fastabend , Jakub Sitnicki Message-ID: <66c7a37fd0270_1b1420837@john.notmuch> In-Reply-To: References: <20240821030744.320934-1-xiyou.wangcong@gmail.com> <20240821145533.GA2164@kernel.org> Subject: Re: [Patch bpf] tcp_bpf: fix return value of tcp_bpf_sendmsg() Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cong Wang wrote: > On Wed, Aug 21, 2024 at 03:55:33PM +0100, Simon Horman wrote: > > On Tue, Aug 20, 2024 at 08:07:44PM -0700, Cong Wang wrote: > > > From: Cong Wang > > > > > > When we cork messages in psock->cork, the last message triggers the > > > flushing will result in sending a sk_msg larger than the current > > > message size. In this case, in tcp_bpf_send_verdict(), 'copied' becomes > > > negative at least in the following case: > > > > > > 468 case __SK_DROP: > > > 469 default: > > > 470 sk_msg_free_partial(sk, msg, tosend); > > > 471 sk_msg_apply_bytes(psock, tosend); > > > 472 *copied -= (tosend + delta); // <==== HERE > > > 473 return -EACCES; > > > > > > Therefore, it could lead to the following BUG with a proper value of > > > 'copied' (thanks to syzbot). We should not use negative 'copied' as a > > > return value here. > > > > > > ------------[ cut here ]------------ > > > kernel BUG at net/socket.c:733! > > > Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP > > > Modules linked in: > > > CPU: 0 UID: 0 PID: 3265 Comm: syz-executor510 Not tainted 6.11.0-rc3-syzkaller-00060-gd07b43284ab3 #0 > > > Hardware name: linux,dummy-virt (DT) > > > pstate: 61400009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) > > > pc : sock_sendmsg_nosec net/socket.c:733 [inline] > > > pc : sock_sendmsg_nosec net/socket.c:728 [inline] > > > pc : __sock_sendmsg+0x5c/0x60 net/socket.c:745 > > > lr : sock_sendmsg_nosec net/socket.c:730 [inline] > > > lr : __sock_sendmsg+0x54/0x60 net/socket.c:745 > > > sp : ffff800088ea3b30 > > > x29: ffff800088ea3b30 x28: fbf00000062bc900 x27: 0000000000000000 > > > x26: ffff800088ea3bc0 x25: ffff800088ea3bc0 x24: 0000000000000000 > > > x23: f9f00000048dc000 x22: 0000000000000000 x21: ffff800088ea3d90 > > > x20: f9f00000048dc000 x19: ffff800088ea3d90 x18: 0000000000000001 > > > x17: 0000000000000000 x16: 0000000000000000 x15: 000000002002ffaf > > > x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 > > > x11: 0000000000000000 x10: ffff8000815849c0 x9 : ffff8000815b49c0 > > > x8 : 0000000000000000 x7 : 000000000000003f x6 : 0000000000000000 > > > x5 : 00000000000007e0 x4 : fff07ffffd239000 x3 : fbf00000062bc900 > > > x2 : 0000000000000000 x1 : 0000000000000000 x0 : 00000000fffffdef > > > Call trace: > > > sock_sendmsg_nosec net/socket.c:733 [inline] > > > __sock_sendmsg+0x5c/0x60 net/socket.c:745 > > > ____sys_sendmsg+0x274/0x2ac net/socket.c:2597 > > > ___sys_sendmsg+0xac/0x100 net/socket.c:2651 > > > __sys_sendmsg+0x84/0xe0 net/socket.c:2680 > > > __do_sys_sendmsg net/socket.c:2689 [inline] > > > __se_sys_sendmsg net/socket.c:2687 [inline] > > > __arm64_sys_sendmsg+0x24/0x30 net/socket.c:2687 > > > __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] > > > invoke_syscall+0x48/0x110 arch/arm64/kernel/syscall.c:49 > > > el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:132 > > > do_el0_svc+0x1c/0x28 arch/arm64/kernel/syscall.c:151 > > > el0_svc+0x34/0xec arch/arm64/kernel/entry-common.c:712 > > > el0t_64_sync_handler+0x100/0x12c arch/arm64/kernel/entry-common.c:730 > > > el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:598 > > > Code: f9404463 d63f0060 3108441f 54fffe81 (d4210000) > > > ---[ end trace 0000000000000000 ]--- > > > > > > Fixes: 4f738adba30a ("bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data") > > > Reported-by: syzbot+58c03971700330ce14d8@syzkaller.appspotmail.com > > > Cc: John Fastabend > > > Cc: Jakub Sitnicki > > > Signed-off-by: Cong Wang > > > --- > > > net/ipv4/tcp_bpf.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c > > > index 53b0d62fd2c2..fe6178715ba0 100644 > > > --- a/net/ipv4/tcp_bpf.c > > > +++ b/net/ipv4/tcp_bpf.c > > > @@ -577,7 +577,7 @@ static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size) > > > err = sk_stream_error(sk, msg->msg_flags, err); > > > release_sock(sk); > > > sk_psock_put(sk, psock); > > > - return copied ? copied : err; > > > + return copied > 0 ? copied : err; > > > > Does it make more sense to make the condition err: > > is err 0 iif everything is ok? (completely untested!) > > Mind to elaborate? > > From my point of view, 'copied' is to handle partial transmission, for > example: > > 0. User wants to send 2 * 1K bytes with sendmsg() > 1. Kernel already sent the first 1K successfully > 2. Kernel got some error when sending the 2nd 1K > > In this scenario, we should return 1K instead of the error to the caller to > indicate this partial transmission situation, otherwise we could not > distinguish it with a compete failure (that is, 0 byte sent). Yep, if we don't return the positive value on partial send we will confuse apps and they will probably resent data. >From my side this looks good. Reviewed-by: John Fastabend > > Do I miss anything? > > Thanks.