From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B8D1F606A332 for ; Wed, 4 Nov 2026 19:27:47 +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=K+qv0mwQ Received: by kanga.kvack.org (Postfix) id AB50E6B05D5; Wed, 4 Nov 2026 14:27:46 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A8B896B05E0; Wed, 4 Nov 2026 14:27:46 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9A29D6B05E1; Wed, 4 Nov 2026 14:27:46 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 6D07E6B05D5 for ; Wed, 4 Nov 2026 14:27:46 -0500 (EST) Received: from smtpin24.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id E12BAC07C4 for ; Wed, 4 Nov 2026 19:27:45 +0000 (UTC) X-FDA: 85398421290.24.B111C4B Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf30.hostedemail.com (Postfix) with ESMTP id 26EBB80002 for ; Wed, 4 Nov 2026 19:27:44 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=K+qv0mwQ; spf=pass (imf30.hostedemail.com: domain of brauner@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=brauner@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793820464; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=8vwIQDZABfbDXUA4Rhtj/FFiRIzet50vFXOLtBzgPyU=; b=V6O7ZPuaqmRwUEpORkqbWpD8kWAp1wcKlYyIKLFYZkGywq8OOBm5V0mcQNdilb+f5hv3LP onvLDwmAHduuoxbxHozXtyCorr4uhN1cwjZw13slFEtIwx3ukP6l60VnM0FRpJsjhmhjrp UjRe1W/UstDo4gn631KHkoSoihzkvIU= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=K+qv0mwQ; spf=pass (imf30.hostedemail.com: domain of brauner@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=brauner@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793820464; b=qC4HJwUNN4tdu0s6oyC8KlWbf8sZZO8KG48B6mLbVwg25+35vdI8h7ennmvkvkoCr88je0 LW/rCUwlQREve4DZeA9vDzNMce0mwRZE5qIVVAKtV95htrNYBMl/LYfz6+Rup/fggHJAuU OkUvXwk/MDnQFGCjBm5Lm5sK0LivTi8= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 6865940510; Wed, 4 Nov 2026 19:27:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BA621F000C1; Wed, 4 Nov 2026 19:27:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793820463; bh=8vwIQDZABfbDXUA4Rhtj/FFiRIzet50vFXOLtBzgPyU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=K+qv0mwQcjtL/qGdS6zLTIdv/G0RXM8xsdMjUnhgG0fNfAYk4b2pJX930sQZnPQep +LPdNInthRhEsKuQKDBplBRNncD5RXDkf1MmvrNYXt/kezR7Og4AukJlDkC+uqQdvQ 3UcyZsZ5M2SCBuJu/oEitA7gekht06is34RQC+0SGBCyvPBf2/f+wRq4YKjtHH607t u2wONuJ6/ShFerskIef6UB1DalfazMx1QVWxa/FYtYmDpi1QxRXXlAEaJ1aaOkdQFG kAOIkXKB/WNg0BuIpmEdndNkSZIlkssgbriZFcnsRM4VXunhgfFvWP2W8uGj5+pKbF w0V3MGDPqlrPQ== From: Christian Brauner To: linux-fsdevel@vger.kernel.org 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-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-um@lists.infradead.org, linux-wireless@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, ntfs3@lists.linux.dev, platform-driver-x86@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-sound@vger.kernel.org, netfilter-devel@vger.kernel.org, dri-devel@lists.freedesktop.org, ibm-acpi-devel@lists.sourceforge.net, jfs-discussion@lists.sourceforge.net, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-cifs@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-mm@kvack.org, linux-sh@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, sparclinux@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-doc@vger.kernel.org, linux-serial@vger.kernel.org, linux-atm-general@lists.sourceforge.net, Takashi Iwai , linux-input@vger.kernel.org, linux-raid@vger.kernel.org, linux-ext4@vger.kernel.org, linux-modules@vger.kernel.org, linux-debuggers@vger.kernel.org, "Christian Brauner (Amutable)" , Chuck Lever Subject: [PATCH RESEND v2 47/51] proc: sysctl: look at the table under sysctl_lock when creating an inode Date: Wed, 4 Nov 2026 20:27:29 +0100 Message-ID: <20261104-work-procfs-bugfixes-v2-47-021c84d852e0@kernel.org> In-Reply-To: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.17-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2783; i=brauner@kernel.org; h=from:subject:message-id; bh=qNc6cmXDzjiIgH+LQmxRb8DpjTAU1o7z7wzEsOSW+y4=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMWS9bmJza0sIPDqr+OtjFeG4XR03HmoLr7n57Jt/hcxie 69L4b9dO0pZGMS4GGTFFFkc2k3C5ZbzVGw2ytSAmcPKBDKEgYtTACbi187wv2hWT/9l9+XPdiy4 Mvm7x6F5LA4Csrv4Z0ak9SrWM8XotDD8M7ASkA469SZgqbzuxov6f2ekegdpRrKw1vJ3ZETYaKT yAAA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit X-Stat-Signature: dzcmfgb4xmxxmmy8rh86ti84nzwixbgg X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 26EBB80002 X-HE-Tag: 1793820464-228564 X-HE-Meta: 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 I3QElfCi Fad9+sNNupXVZy2BhyDIzoStzc/wiSjDKEwHP8tBbbmbkVm/+lzPD9Y1sOsT4JDkpy6TcPLX+SqHlwATqxosYN5dfBtQfJ0Er1kPPhF0LXO7gsznrP802YlSznyvc9rCM0qDts7vfXuJDyMQH4Crby5aoBcD2bVgwl/ep/2etxoklJOL/uRQY8Gac7w/oHp+puFVUCxIDs3KshW9tyOns4zPmjQV/XX391+EZjDOK++lH+5Hw35/OxgFblEoGrguBapjS3zlzNTViQT6SWowZkmSbAWlGonsH4NPv9n//qNFQFampbvhy2Eqs4fgLpqVP/MzXd1YK891yFWiuqOyCyVvLpuu2ugbAF70vGeC+iN6VVYOB5RIsQOIlmrILcSsjrjZEcBe7wkTCTZ7H6UXtLqxvgSbIts1T1bWPW9SUZAp+eb/066Zn/Fku2DBmG4EHWtDaSh0FP3JiqNKo7DCECK0O9k0BFf7WHYrg Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 proc_sys_make_inode() checks under sysctl_lock that @head isn't being unregistered, lets go of the lock, and then reads the mode of @table and calls ->set_ownership() with @head. That's fine as long as the caller holds @head in use, which keeps unregistering from getting past that check. The next patch has a caller that only pins the memory of @head. For that one the table, and whatever the owner of the header keeps behind it, is only there for as long as nobody unregisters the header, which happens under sysctl_lock. So read the mode and set the ownership before letting go of the lock. The ->set_ownership() callbacks only look up ids in a user namespace. No functional changes. Signed-off-by: Christian Brauner (Amutable) --- fs/proc/proc_sysctl.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index f5c9f04e8509..82024f1ea756 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -500,6 +500,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, struct ctl_table_root *root = head->root; struct inode *inode; struct proc_inode *ei; + umode_t mode; inode = new_inode(sb); if (!inode) @@ -509,12 +510,22 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, ei = PROC_I(inode); + inode->i_uid = GLOBAL_ROOT_UID; + inode->i_gid = GLOBAL_ROOT_GID; spin_lock(&sysctl_lock); if (unlikely(head->unregistering)) { spin_unlock(&sysctl_lock); iput(inode); return ERR_PTR(-ENOENT); } + /* + * The table, and whatever the owner of the header keeps behind it, + * is only there for as long as nobody unregisters the header, which + * happens under sysctl_lock. So look at them before letting go of it. + */ + mode = table->mode; + if (root->set_ownership) + root->set_ownership(head, &inode->i_uid, &inode->i_gid); ei->sysctl = head; ei->sysctl_entry = table; hlist_add_head_rcu(&ei->sibling_inodes, &head->inodes); @@ -522,8 +533,8 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, spin_unlock(&sysctl_lock); simple_inode_init_ts(inode); - inode->i_mode = table->mode; - if (!S_ISDIR(table->mode)) { + inode->i_mode = mode; + if (!S_ISDIR(mode)) { inode->i_mode |= S_IFREG; inode->i_op = &proc_sys_inode_operations; inode->i_fop = &proc_sys_file_operations; @@ -535,11 +546,6 @@ static struct inode *proc_sys_make_inode(struct super_block *sb, make_empty_dir_inode(inode); } - inode->i_uid = GLOBAL_ROOT_UID; - inode->i_gid = GLOBAL_ROOT_GID; - if (root->set_ownership) - root->set_ownership(head, &inode->i_uid, &inode->i_gid); - return inode; } -- 2.53.0