From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-il1-f175.google.com (mail-il1-f175.google.com [209.85.166.175]) (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 A11427DA62; Thu, 15 Aug 2024 10:48:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.166.175 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723718935; cv=none; b=YuFCl8CDai9Hy0fxUqIx7594+UxmkN5FYxUHXlqa8sKJNMB8/4C2WzRiHlB8BuRsynDXLoCFqPZ0Nz+WCqbd0Ueh+xPexpEXpTrEdCQWlkbbXRG0somhByZny3F858AgIgE0JQxc1ybwFARm9JEt7HvpldqFKEmvNP+OiJJWO0g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723718935; c=relaxed/simple; bh=GyDD3yza3z6x3taZ8nX69f5bL4Rz4uQTO9+7tRRZBsA=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=tTW+D2ksEa5xmnrYJ6YfPhjCA1myU3w5gb/3jloTHPMKXIkG9zndwarUlZ6R/fOxUzC3Se8kWY05pspZ1+TVRQPJNbx6GBZJu6sTXJYwio6QRBZP+VYluB0DASE3LZcatO7uFtlZYlPbabGK7/xzB4I2Ow13PhETnyVXuUMa9c4= 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=Xryd6LvA; arc=none smtp.client-ip=209.85.166.175 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="Xryd6LvA" Received: by mail-il1-f175.google.com with SMTP id e9e14a558f8ab-39b06af1974so3189335ab.2; Thu, 15 Aug 2024 03:48:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1723718932; x=1724323732; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=uItcCny5ZpkIJczdfFLsxnmfv2Non+oTHPGtPs4FhnI=; b=Xryd6LvApKhb9qzR9kk48MmpgWX8+/MIY34ajibFaIWaPPq5NyrEyRMm2NPtmkPjrS i+Ka2i5Pa8NbcHKHSCAmytuWdLWbfK+SSJwJZOHzx0Ip4fun2/tMQbuTvKywjggyXDyf ao0K4Zy9W7o0stHG+S5zDf+yxV7aM/KLLhmJ1wS2I/+1ZfnB3WwfJLlPkVMeQIED+Hg8 cod4VTQkmKhUvvu2f6NxvQUaoW0fJ/pDTVvKb9EH2a58G2RTHDecT84sOD16+kojiac8 em+jM5gt+XR7eL5Yz0jHs1VLAxihISSd/46qD4bSyxvTUzdknD/Mz2DiCVmyaHbOqTdl e7TA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1723718932; x=1724323732; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=uItcCny5ZpkIJczdfFLsxnmfv2Non+oTHPGtPs4FhnI=; b=uS+wgjEd/rfWvwCR7QPe0J7LNvTbtAM+KBOfPfEungdaLeggfhqdtc+C62D1AI/UsZ ERb6tjazxYRs6uVTMw6SUBLtuv9FZlaPcFdlJ/XgCZDHYAU4fKl+DdNobgZEBOdStCYm OdPWZbjZKfwsX/FjdtaG6dRfrxXNXcz5wIkRiPn+l4icFhGOy/h7gCxHrjY0gTbXRYAF pwK0bUbgL2quMN7RscQaWkb1netKNWY6vAOOYsKhHqAk4FZBD5f8HEZCkaixWLGsdQnL 1dbAgE0+UtFG7VyRQvQ9qm8Os5PytbG7I7sqwV47Wn9yz2osivrYa0y522GY6Q8onkGZ USgg== X-Forwarded-Encrypted: i=1; AJvYcCV3SRacDCz6iahrj8m4STQzKAIiCdL8Y+8sgZ0JEL5LKGzjAnfYxgvrxv2dMY3M3wIVFxIXRGrlQMLzdQxf3DpCo2FiTbKUJTqlkUxwoTyahquWmrEJiYvaPM1DQZcOsgSTrpwk X-Gm-Message-State: AOJu0YyZAx6LsNC61hkMlOkK8Jl8nZ9sFWXaUZAbNMpLyRBkDkpOwoJr BcEq2Tnii1eUGANYcfNtmai00NaDi7z2dcHhwFFZzVO3JCgAUAvyTMftx2QamHLLLNosj58BVnc 64HbArpkg14deDM2Vrs8X4Y4IJ90= X-Google-Smtp-Source: AGHT+IFusiwxIxLhiiogzhKzID2xdWRdUbfeoUs5+6sigFZbG7D0YWWmTp0XuHTKZKmbr6q0+okAIhHR8voqz+7tdI8= X-Received: by 2002:a92:c24f:0:b0:39a:ea86:d615 with SMTP id e9e14a558f8ab-39d124412a0mr66843225ab.6.1723718932601; Thu, 15 Aug 2024 03:48:52 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20240815084330.166987-1-sunyiqixm@gmail.com> In-Reply-To: <20240815084330.166987-1-sunyiqixm@gmail.com> From: Jason Xing Date: Thu, 15 Aug 2024 18:48:16 +0800 Message-ID: Subject: Re: [PATCH] net: remove release/lock_sock in tcp_splice_read To: sunyiqi Cc: edumazet@google.com, davem@davemloft.net, dsahern@kernel.org, kuba@kernel.org, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, Aug 15, 2024 at 5:46=E2=80=AFPM sunyiqi wrote= : > > When enters tcp_splice_read, tcp_splice_read will call lock_sock > for sk in order to prevent other threads acquiring sk and release it > before return. > > But in while(tss.len) loop, it releases and re-locks sk, give the other > thread a small window to lock the sk. > > As a result, release/lock_sock in the while loop in tcp_splice_read may > cause race condition. > > Fixes: 9c55e01c0cc8 ("[TCP]: Splice receive support.") > Signed-off-by: sunyiqi It's more of an optimization instead of a BUG, no? I don't consider it as a bug, unless you can prove it... Let me ask what kind of race issues could re-lock cause? I think holding the socket lock too long is not a good idea because releasing the lock can give others breathing (having the chance to finish their own stuff). Please see release_sock(). Thanks, Jason > --- > net/ipv4/tcp.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index e03a342c9162..7a2ce0e2e5be 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -856,8 +856,6 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *= ppos, > > if (!tss.len || !timeo) > break; > - release_sock(sk); > - lock_sock(sk); > > if (sk->sk_err || sk->sk_state =3D=3D TCP_CLOSE || > (sk->sk_shutdown & RCV_SHUTDOWN) || > -- > 2.34.1 > >