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=1793907025; b=nmu3vc3AQa0/0fkkNylRAdbJ5aiS6+Sc+xrI6YORnVCn9N5GhwzxNxw5xgZfy/vhE/nT i+1fHaW7jGPJJcPXIyQ8VpKwmmgKrLgmjMrhjB6GWkwVyBQEcasVamXNt6VD7csMu6Wnn ajlQ/ay0OtB6/usN5ZUYohT1E6N1HQffOKtSippUwKLtdTZhcOnlWY93qmwdrQyUbo+Mi bOA5PlTMaoKkwONGPo0XX+C4zHoTo9EbUpj0+qRXM/VTy6kM9gk1ad6TUkgthi/M5alz7 mDNOq9kIPdmwXA/596hsHTfUkEhKL6CgBVIppUkEmNSvMdW08iD5EaF/AJYh/kNTF1g== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793907025; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=2ZEFR6gjnP3wVSksugK0Xi/aHT+AN/UQkRBLfUojuMA=; b=Udq8ePYyq2vBnXecrQLvf6Y5YO00oK713LxSo0hSpJTmEGQZOhD1HynX8PwPRmT8rOnL 2s9oVlc3+fxXKTWCqMNpAJ5/Vk+xgrxcyhkAi3/qFkwEz1n5fhEzmqlOrE/a6GCvXTAeO yo4Jz8+thkv35rD8eRS16WF2LNrQRpsTQZdJqo1VAlUj5MHkuHk1Io1vZAGhwy7Ft2xVq vbn/rImksLrFAYXMXUwIoT9G7A4/dZqvmUSQY54fLXTqqpYAHuQmIGGrVSJq4o7VSAH9f MzZoHte01/sQ5LqQtzLLdj7TB3ev6NDzuaDZ6JljvJvE2kDmXbMnIaKNyby0bwQ7dCQ== 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=aFb5Yznl; 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 0D6AB606B9C7; Thu, 5 Nov 2026 19:30:25 +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=aFb5Yznl Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C2801F00919; Thu, 5 Nov 2026 19:30:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793907024; bh=2ZEFR6gjnP3wVSksugK0Xi/aHT+AN/UQkRBLfUojuMA=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=aFb5YznlYnipR19+u+Im8pSQa+/x3WULY7AoYCqTywnkISPlw9ZNAM38Fkr0pYgvi 6cp1ijVNCZRYHKjlbb7mp7pruaep/7wtvEt054PrL+Zxw8V6yne8Cd+u9HQSVVaeWR /crGUSwOp+7vR5Uci9LlccyoZkEnJUeSmLK9Ve7s/+EFwq4GsVFjKdQehhVg+5wuGX w0RgAwmJ2guiBQr2AyG8R5mOMd+mWgU2cUDkOUbrm62IVqlgFWh8+X0/UvbreN6eUd orSAqTkhmHMjsXQrmyGsTaiwsc4DUpcbRA79TZz6uGLjaUzMpDTmJ0UWgvZ1kT77o6 QnN26MXG0YM6A== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RESEND v2 46/51] proc: sysctl: copy to and from userspace without holding the table 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-v2-46-021c84d852e0@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> <20261104-work-procfs-bugfixes-v2-46-021c84d852e0@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 05 Nov 2026 19:30:23 +0000 X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > proc_sys_call_handler() grabs the table, copies in what is written, > calls the handler and copies what it produced out to userspace before > it lets go of the table again. Unregistering a table waits until nobody > uses it anymore. So a reader or writer whose copy faults for as long as > it wants, with userfaultfd or a stalled FUSE mapping, keeps > unregister_sysctl_table() waiting, and its callers like to hold locks > while they do that. addrconf unregisters the ipv6 sysctls of a device > with RTNL held, so a stalled read of /proc/sys/net/ipv6/conf//mtu > holds up every RTNL user until the reader gives up. >=20 > Copy in before grabbing the table and copy out after letting go of it, > like procfs and kernfs do for their files. The buffer is ours, nothing > needs the table for the copies. >=20 > That moves the allocation and the copy in before the permission check. > A write that can't be copied in, or a request that is too large, now > fails with -EFAULT or -ENOMEM where it used to fail with -EPERM. >=20 > Fixes: 330d57fb98a9 ("[PATCH] Fix sysctl unregistration oops (CVE-2005-27= 09)") > 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=3D46