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 197F5143736; Fri, 23 Aug 2024 08:25:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724401527; cv=none; b=Wmm5Mb3VtlcMqVsi1dginN3fjZNvG5JLetLUVfneFU4bGMM5BP4m5UNNhbYEVe2asGXKXYcqcI09qARWJZqFPHAvbwdR0x+x0TOM50h8kGiQ3rGZ01W5Yi4GCNLnvQQ1+TAUYXmq6pTJWwIYwaeJikEbB6rT2VTZDuCL9qFOkMo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724401527; c=relaxed/simple; bh=BHLpzt7Dtjn8m5qYRc3cu8T6nysZSnMVb3D3BT0zxgE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YpZ54ryr12KGNzG1U382XQ7fSwvkJYmpingpWox8bQkb4xeyDiMWzU2uuqXp7M8sHZewjy2IMPgVSLvASCP/+GA8xd0WtAEdEPvOGkk3k/Z7GL+kM3E0uAFLRvb9jxAGGlN1MuQaihyg3ZG5mhotoY2ib99t58AzHiOlqW1gcHI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EOC7GR17; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EOC7GR17" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16C6EC32786; Fri, 23 Aug 2024 08:25:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724401526; bh=BHLpzt7Dtjn8m5qYRc3cu8T6nysZSnMVb3D3BT0zxgE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EOC7GR17b6q0+eIL7+qodYXvZFuHW7zLU7DE9si/AJdiIY3EskirzXlR3wTxAUNCn jqfQ37LgoKdlHLFr3QLMyM5Z/1k/ZlGHeF/hm+1+p0AP5KBPJ7bEE+gLUc3DKK3hrJ HgbkOswszxanj4Vepy6HGt/V0xSQSm76KY8FdY8CZvvV2jsZfQF8cdpMYEq0FsOtXY 81LmQjhy2A72QJXDlk9aC7bOxmqcTgEvJ+emOB5kIMWZm4oZwUn85OBoxdrdBduXCY q0Z+S9ClP3LCDq7nKNa8JOba6bNVNG/OpyIHM7RWcVEga9RAVH2huZ7Sw7n+TxmPlQ lhgISgzdXrl9g== Date: Fri, 23 Aug 2024 09:25:22 +0100 From: Simon Horman To: John Fastabend Cc: Cong Wang , netdev@vger.kernel.org, bpf@vger.kernel.org, Cong Wang , syzbot+58c03971700330ce14d8@syzkaller.appspotmail.com, Jakub Sitnicki Subject: Re: [Patch bpf] tcp_bpf: fix return value of tcp_bpf_sendmsg() Message-ID: <20240823082522.GS2164@kernel.org> References: <20240821030744.320934-1-xiyou.wangcong@gmail.com> <20240821145533.GA2164@kernel.org> <66c7a37fd0270_1b1420837@john.notmuch> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <66c7a37fd0270_1b1420837@john.notmuch> On Thu, Aug 22, 2024 at 01:45:51PM -0700, John Fastabend wrote: > 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? I was thinking that a valid test for for being in an error state is that err is non-zero. Although given the below, it seems that I was mistaken. > > > > 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 Thanks for responding to my query. FWIIW, I am now happy with this patch.