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 EA00F1B4231 for ; Mon, 16 Jun 2025 14:09:32 +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=1750082973; cv=none; b=YKh/OjBmCAVa7UjaEK3t/e2ElJdCGQ2sBkOW+5loEfkyZMmJRkvbbeHvfbqOGYFgqvRMqVYawgwuJWMY2gJ6cneBvGPFDsqyWnhVcnaIhH6z6xS71LbbIrrTq64uii7Lxzi8xZgSfaYwf7YLx7fh3yAyZ6Xp1Utxk9W+ibFPgbU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750082973; c=relaxed/simple; bh=Z38iWUKwPy08Mg6Mg4GfZfkb+ktx5UqaAE2UbcOC8Lk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uTlzTUGYybB3JCunQYEsAwm82UvERCBKtKQPL2HWr7jjeN4wnjmZz3qfY7P0PHoXM9OUax8XTXTDp95yMbw0n/kMLGxS43RoN8kltckTCOfk9M+bipZ99bBapNtjnPk51u32LesTv9qyTHFtYJq5dIoWotbUqJ1MevBcL4hF13o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=M+TpS13o; 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="M+TpS13o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 73340C4CEEA; Mon, 16 Jun 2025 14:09:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750082972; bh=Z38iWUKwPy08Mg6Mg4GfZfkb+ktx5UqaAE2UbcOC8Lk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M+TpS13obVGKSMRt10ShFgmZ6NEWlbv7QinufND6esN3JNiizuh8XNUQPKFsBE3AX iJ+iwagYM/bnka66IJBIWjs0Qki6ia4GQiRlcblV1UNalcpm+4IMVG80b5cCogkkal qtHkBdz15Jxr5omiF7DrmNscgHE/kjyYLYpFyEvXuWq6lL7WuvZNjSprupAxp6RFdh Adciseb82ETt3git7vlUFMiW+nJ2JT48BdWP0X6dROdEUkvbSwGcAxzpHExe241im3 +RxmtDREb7dGtBSCoo6rbLUHyiM4g4tSqi5MnMPAnrbYYMDsbSWueigd0II6N3x/O6 jATczdwNQI4cg== Received: from johan by xi.lan with local (Exim 4.97.1) (envelope-from ) id 1uRAWf-000000003Fc-1fPG; Mon, 16 Jun 2025 16:09:30 +0200 Date: Mon, 16 Jun 2025 16:09:29 +0200 From: Johan Hovold To: Kuniyuki Iwashima Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Kuniyuki Iwashima , Christian Heusel , =?utf-8?B?QW5kcsOp?= Almeida , netdev@vger.kernel.org, Jacek =?utf-8?Q?=C5=81uczak?= Subject: Re: [PATCH v1 net] af_unix: Allow passing cred for embryo without SO_PASSCRED/SO_PASSPIDFD. Message-ID: References: <20250611202758.3075858-1-kuni1840@gmail.com> 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-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250611202758.3075858-1-kuni1840@gmail.com> On Wed, Jun 11, 2025 at 01:27:35PM -0700, Kuniyuki Iwashima wrote: > From: Kuniyuki Iwashima > > Before the cited commit, the kernel unconditionally embedded SCM > credentials to skb for embryo sockets even when both the sender > and listener disabled SO_PASSCRED and SO_PASSPIDFD. > > Now, the credentials are added to skb only when configured by the > sender or the listener. > > However, as reported in the link below, it caused a regression for > some programs that assume credentials are included in every skb, > but sometimes not now. > > The only problematic scenario would be that a socket starts listening > before setting the option. Then, there will be 2 types of non-small > race window, where a client can send skb without credentials, which > the peer receives as an "invalid" message (and aborts the connection > it seems ?): > > Client Server > ------ ------ > s1.listen() <-- No SO_PASS{CRED,PIDFD} > s2.connect() > s2.send() <-- w/o cred > s1.setsockopt(SO_PASS{CRED,PIDFD}) > s2.send() <-- w/ cred > > or > > Client Server > ------ ------ > s1.listen() <-- No SO_PASS{CRED,PIDFD} > s2.connect() > s2.send() <-- w/o cred > s3, _ = s1.accept() <-- Inherit cred options > s2.send() <-- w/o cred but not set yet > > s3.setsockopt(SO_PASS{CRED,PIDFD}) > s2.send() <-- w/ cred > > It's unfortunate that buggy programs depend on the behaviour, > but let's restore the previous behaviour. For the record, this one fixes the wlroots and Xorg crashes on USB-C DisplayPort Altmode hotplug that I hit consistently with 6.16-rc1 on machines like the Lenovo ThinkPad X13s and T14s. > Fixes: 3f84d577b79d ("af_unix: Inherit sk_flags at connect().") > Reported-by: Jacek Łuczak > Closes: https://lore.kernel.org/all/68d38b0b-1666-4974-85d4-15575789c8d4@gmail.com/ > Signed-off-by: Kuniyuki Iwashima Johan