From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793907029; b=K7PAqft9wIMdljuXKRG7d++VGFwzhkFLJma8GppuDBmR7RDfowE42Epa2oB4XzYM6N6t xHxJfcCNXouQB7MYOb6nGNX6eR8wUR8QJNLy2d/EkugM1V7m4aepJMvfTm00EJcGDdUky VOwxKs+9x17XnMuvp6BFbNj97XDfwMCWOD1/GJMYaZmWPPoV80+1DdXtLoWjnY9N1+M5+ RCY/DcL7oSEzszyWGdyYQebHwDz31pNiZCwdgtxcBrfrLTDEQXGtlEIPis8ajXhxrveO3 7+P9mPW5R6nriQ/hVAIpWlN7gCtrS1A4GFdf9encxmvcPr3AAmkQ616xORxJtQr0Buw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793907029; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=TUEa7eIRLkYlG50VJyzFVsWpbL0zjSyXV5JMm1JJ87k=; b=RRA2GTDcIPQHue/19b5cKK2TayYvmMJFuumie/Y0d1BC2t2UcFMmjwzxEa41juGRtlyQ AZ51TKYi1j9S6qy+UduCq8zgGI7f09VfrAOd9Yz+V+MtZDdSnA4/NxZDHNOTWyzklqOuu wG+qmTx/RRZ4h/IjrLk+BxX+SaPXNtxuN/Z1UdGntdEOW8YvWnNRTfj+PLaFfXJh2biZc cbLQNKYpPr9/A71UwxUHf0RNLuz6F2Edp39wE1rhB9n1zIrJLBwjZWvmF2yNgiqCILoSG L55VCfa5R15U0g5+h5E2tqgdsZ9iDWxyhVYCuoGOSvfw3wSOLpIfxdmtsj7G9yqyBQQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="EzE5K//c"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44FCA606A336; Thu, 5 Nov 2026 19:30:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=EzE5K//c Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54F291F00A02; Thu, 5 Nov 2026 19:30:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793907028; bh=TUEa7eIRLkYlG50VJyzFVsWpbL0zjSyXV5JMm1JJ87k=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=EzE5K//cJCfees6tq1n/aL2ZXIFBE5phY+UQOmHq0vN8UPvYS/t9kkzR12V91SBSS mhS7JX+wWb8SSFsgjQLGWb/WG0xY7lURsW1aoepv/YNSVEiw0q1fXhrM33YsC2iYcX Y+waIrwUG/i8Vo4xsrxYyrlh/w1ZXi6PT5QOp69R3v0bZCzhRKgl7jMf/20Nx+KlzW 0im/yzY5zXpuAl+QtNTMGdrxcjVY3ep9xLEZXfFos47R/RaVosKingXECZ1lFQe2/a 3/8aSX9eI5PmGSLMxslCDj4GFhqROFpYezwD6KMYwTFTCdln5UIo/LVBxVD2dGdOQo DMN8N2/pVc/WQ== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RESEND v2 48/51] proc: sysctl: don't hold the tables while readdir copies to userspace Reply-To: sashiko-reviews@lists.linux.dev To: "Christian Brauner" Cc: "Linus Torvalds" , "Jann Horn" , "Josef Bacik" , "Chris Mason" , "Jeff Layton" , NeilBrown , "Eric Dumazet" , "Thomas Gleixner" , "Al Viro" , "Jonathan Corbet" , "Christoph Hellwig" , "Greg Kroah-Hartman" , "Joel Granados" , "Kees Cook" , "Jan Kara" , "Jan Kara" , linux-s390@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, linux-m68k@lists.linux-m68k.org, linux-serial@vger.kernel.org, "Takashi Iwai" , linux-ext4@vger.kernel.org, "Chuck Lever" , tytso@mit.edu, "Heiko Carstens" , "Vasily Gorbik" , "Alexander Gordeev" , "Christian Borntraeger" In-Reply-To: <20261104-work-procfs-bugfixes-v2-48-021c84d852e0@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> <20261104-work-procfs-bugfixes-v2-48-021c84d852e0@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 05 Nov 2026 19:30:26 +0000 X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > proc_sys_readdir() holds the directory's table for the whole readdir > and the table of each entry while dir_emit() copies its name to > userspace. Unregistering a table waits until nobody uses it anymore. So > a getdents64() whose buffer faults for as long as it wants keeps > unregister_sysctl_table() waiting, just like a stalled read() does. > Listing /proc/sys/net/ipv6/conf// that way holds up the removal of > the device under RTNL. >=20 > So don't take any table into use for a listing. A header counts what > refers to its memory, the inodes made for it, and unregistering doesn't > wait for those. readdir takes one of those references on the entry it is > at instead, which keeps the header around and nothing else. Under > sysctl_lock, where unregistering erases an entry, it finds the entry, > copies its name, follows a link to the entry it stands for and pins > that. Then it looks the dentry up, creates the inode if there is none, > [ ... ] > directory was done. >=20 > Fixes: 77b14db502cb ("[PATCH] sysctl: reimplement the sysctl proc support= ") > Cc: stable@vger.kernel.org > Signed-off-by: Christian Brauner (Amutable) Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261104-work-procf= s-bugfixes-v2-0-021c84d852e0@kernel.org?part=3D48