From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-fw-52002.amazon.com (smtp-fw-52002.amazon.com [52.119.213.150]) (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 D4246632; Wed, 21 May 2025 00:42:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.119.213.150 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747788146; cv=none; b=hCNsbkACdpx5pnWFk6FBckkyUETTust00XMrI4ooOuYcinW8r2g9alE1w7SmJdXXGSfuf8Fy5F3z7vSR3q8BAZnJFIrhnxFJIQOkcFnkGvGAH8QW3hhuZtN/VaivC1BLRTr4+qwQNYO4PCa5cGNNF6TFK58ThajN4+Zj7COgEYg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747788146; c=relaxed/simple; bh=JwuXcIJf4i76I1tCA4AmICXNLN6bpvr5vhDsldPaZj4=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=dj7jp5oXP8q9Ot7VwK9N9H5EkyF1PHw3zeX78ppnznEQ3VKkuQCAcnDqbHnxXNstGAUGsB9Oa4e2rBXx4Jrp3LouFvtiFliRFUSW4L54coekQZBRcLcwwhkyR5BB2+Nw2wxJiQtasxHiH8fVnFPdRFsUpp2BLdYBNeDfwiByuso= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.co.jp; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b=MO66rSpd; arc=none smtp.client-ip=52.119.213.150 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.co.jp Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amazon.com header.i=@amazon.com header.b="MO66rSpd" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazoncorp2; t=1747788146; x=1779324146; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=9lVsmYxOW62soy44KdVJkVW7koejhz4/tgmlApVUKS8=; b=MO66rSpdv0klA7RcJ+Ka/gakG0oUkgybgkGgwbWHuSYj0n0yKRcVAXxU 0oDxCBrPWLL7OCyle34dE6MtHmq722KEUbPdDiGkz5OsaYsbHXpNF7I/T PjuL4p1EtrV8gYQX9e1Cq2PrsMplf9rrOlItizwNsTmJ8XMgPtSjd/DuC sHO/puuuxxpf+EewVx9VBxExz96qiPhNvMAB4PR7CAWZuDfCDaf4wP+8W UbEIRWCiFvGNiaQrSSVB9MWRCzag0CxDlUpyIs5boR9eKex//zT0nyAuh /ersy2CevY7axGFKUstk3SJBPs79FMf/RBLR4W45XAu6Q4rBEus/6AXfB A==; X-IronPort-AV: E=Sophos;i="6.15,303,1739836800"; d="scan'208";a="724880082" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.43.8.6]) by smtp-border-fw-52002.iad7.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 May 2025 00:42:21 +0000 Received: from EX19MTAUWC001.ant.amazon.com [10.0.21.151:53710] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.11.48:2525] with esmtp (Farcaster) id e61ff1ca-97b4-4607-8771-aa879e1cc1a9; Wed, 21 May 2025 00:42:19 +0000 (UTC) X-Farcaster-Flow-ID: e61ff1ca-97b4-4607-8771-aa879e1cc1a9 Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX19MTAUWC001.ant.amazon.com (10.250.64.174) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Wed, 21 May 2025 00:42:19 +0000 Received: from 6c7e67bfbae3.amazon.com (10.187.171.41) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Wed, 21 May 2025 00:42:15 +0000 From: Kuniyuki Iwashima To: CC: , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v8 0/9] coredump: add coredump socket Date: Tue, 20 May 2025 17:41:58 -0700 Message-ID: <20250521004207.10514-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250520122838.29131f04@hermes.local> References: <20250520122838.29131f04@hermes.local> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: EX19D040UWB003.ant.amazon.com (10.13.138.8) To EX19D004ANA001.ant.amazon.com (10.37.240.138) From: Stephen Hemminger Date: Tue, 20 May 2025 12:28:38 -0700 > On Fri, 16 May 2025 13:25:27 +0200 > Christian Brauner wrote: > > > Coredumping currently supports two modes: > > > > (1) Dumping directly into a file somewhere on the filesystem. > > (2) Dumping into a pipe connected to a usermode helper process > > spawned as a child of the system_unbound_wq or kthreadd. > > > > For simplicity I'm mostly ignoring (1). There's probably still some > > users of (1) out there but processing coredumps in this way can be > > considered adventurous especially in the face of set*id binaries. > > > > The most common option should be (2) by now. It works by allowing > > userspace to put a string into /proc/sys/kernel/core_pattern like: > > > > |/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h > > > > The "|" at the beginning indicates to the kernel that a pipe must be > > used. The path following the pipe indicator is a path to a binary that > > will be spawned as a usermode helper process. Any additional parameters > > pass information about the task that is generating the coredump to the > > binary that processes the coredump. > > > > In the example core_pattern shown above systemd-coredump is spawned as a > > usermode helper. There's various conceptual consequences of this > > (non-exhaustive list): > > > > - systemd-coredump is spawned with file descriptor number 0 (stdin) > > connected to the read-end of the pipe. All other file descriptors are > > closed. That specifically includes 1 (stdout) and 2 (stderr). This has > > already caused bugs because userspace assumed that this cannot happen > > (Whether or not this is a sane assumption is irrelevant.). > > > > - systemd-coredump will be spawned as a child of system_unbound_wq. So > > it is not a child of any userspace process and specifically not a > > child of PID 1. It cannot be waited upon and is in a weird hybrid > > upcall which are difficult for userspace to control correctly. > > > > - systemd-coredump is spawned with full kernel privileges. This > > necessitates all kinds of weird privilege dropping excercises in > > userspace to make this safe. > > > > - A new usermode helper has to be spawned for each crashing process. > > > > This series adds a new mode: > > > > (3) Dumping into an AF_UNIX socket. > > > > Userspace can set /proc/sys/kernel/core_pattern to: > > > > @/path/to/coredump.socket > > > > The "@" at the beginning indicates to the kernel that an AF_UNIX > > coredump socket will be used to process coredumps. > > > > The coredump socket must be located in the initial mount namespace. > > When a task coredumps it opens a client socket in the initial network > > namespace and connects to the coredump socket. > > > There is a problem with using @ as naming convention. > The starting character of @ is already used to indicate abstract > unix domain sockets in some programs like ss. > And will the new coredump socekt allow use of abstrace unix > domain sockets? The coredump only works with the pathname socket, so ideally the prefix should be '/', but it's same with the direct-file coredump. We can distinguish the socket by S_ISSOCK() though.