From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC4C8C4332F for ; Mon, 17 Oct 2022 15:09:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231326AbiJQPJg (ORCPT ); Mon, 17 Oct 2022 11:09:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56732 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231716AbiJQPJJ (ORCPT ); Mon, 17 Oct 2022 11:09:09 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C896752475; Mon, 17 Oct 2022 08:08:58 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 16A4E611B1; Mon, 17 Oct 2022 15:08:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF510C433D6; Mon, 17 Oct 2022 15:08:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666019306; bh=Ir0kXcjNjtvkOzMmaIP9Gkc1umKgPAQzXSnQF4Hx0lw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WllwBpQhyBft21cOxEgMZNBRGeGn+TQd216+jHa7jgMegzPG3OF4vYhqwtl5lxx8J HswAAwhqusByAmo41hpVVOkDtMe1BaZQ62GAwH5UjO/jTIsNHB7LA/+loHnc286mxP PBuZck5ZygtLLdGNw64NEgritRXMwcMIP2AgbBDMg5dU9dKT04+WFZdZqoqHBEsRRr O0QQ7igOqOpBOMZtGPO+brNw7nTAH28F1eBlQPYedlhfK3oAz+L7DuWmqJkXeZeDEp qPAg//kEahz+7vLmFSKrqi/mDy5pE+GHD+MrAeAhONIPvG7mn2DWy+nsyrAQdkt9F9 SIU6NCcNJoHTQ== From: Christian Brauner To: Amir Goldstein , Miklos Szeredi , "Darrick J . Wong" Cc: Christian Brauner , Al Viro , Christoph Hellwig , Seth Forshee , Yang Xu , Filipe Manana , linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v4 1/6] attr: add in_group_or_capable() Date: Mon, 17 Oct 2022 17:06:34 +0200 Message-Id: <20221017150640.112577-2-brauner@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221017150640.112577-1-brauner@kernel.org> References: <20221017150640.112577-1-brauner@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4395; i=brauner@kernel.org; h=from:subject; bh=Ir0kXcjNjtvkOzMmaIP9Gkc1umKgPAQzXSnQF4Hx0lw=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMST75mcv4t7tZsz1eXLRpLj5s879+6M/Qdp6fua6vKRdpVKC wprvO0pZGMS4GGTFFFkc2k3C5ZbzVGw2ytSAmcPKBDKEgYtTACaydS/DXznnL5IREi/9D94441d05F y46AtPbZO/KVvebblZIVe80oqRYbZ3poPfq46bF1dUJtRmTtJk7Xj/c8e7Kcve/K27oRE5nQsA X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org In setattr_{copy,prepare}() we need to perform the same permission checks to determine whether we need to drop the setgid bit or not. Instead of open-coding it twice add a simple helper the encapsulates the logic. We will reuse this helpers to make dropping the setgid bit during write operations more consistent in a follow up patch. Reviewed-by: Amir Goldstein Signed-off-by: Christian Brauner (Microsoft) --- Notes: /* v2 */ patch added /* v3 */ Amir Goldstein : - Return 0 or ATTR_KILL_SGID to make all dropping helpers behave similarly. /* v4 */ Christian Brauner : - Rename helper to in_group_or_capable() and use it in mode_strip_sgid() as well getting rid of the code duplication. fs/attr.c | 10 +++++----- fs/inode.c | 28 ++++++++++++++++++++++++---- fs/internal.h | 2 ++ 3 files changed, 31 insertions(+), 9 deletions(-) diff --git a/fs/attr.c b/fs/attr.c index 1552a5f23d6b..b1162fca84a2 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -18,6 +18,8 @@ #include #include +#include "internal.h" + /** * chown_ok - verify permissions to chown inode * @mnt_userns: user namespace of the mount @inode was found from @@ -140,8 +142,7 @@ int setattr_prepare(struct user_namespace *mnt_userns, struct dentry *dentry, vfsgid = i_gid_into_vfsgid(mnt_userns, inode); /* Also check the setgid bit! */ - if (!vfsgid_in_group_p(vfsgid) && - !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) + if (!in_group_or_capable(mnt_userns, inode, vfsgid)) attr->ia_mode &= ~S_ISGID; } @@ -251,9 +252,8 @@ void setattr_copy(struct user_namespace *mnt_userns, struct inode *inode, inode->i_ctime = attr->ia_ctime; if (ia_valid & ATTR_MODE) { umode_t mode = attr->ia_mode; - vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode); - if (!vfsgid_in_group_p(vfsgid) && - !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) + if (!in_group_or_capable(mnt_userns, inode, + i_gid_into_vfsgid(mnt_userns, inode))) mode &= ~S_ISGID; inode->i_mode = mode; } diff --git a/fs/inode.c b/fs/inode.c index b608528efd3a..55299b710c45 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -2487,6 +2487,28 @@ struct timespec64 current_time(struct inode *inode) } EXPORT_SYMBOL(current_time); +/** + * in_group_or_capable - check whether caller is CAP_FSETID privileged + * @mnt_userns: user namespace of the mount @inode was found from + * @inode: inode to check + * @vfsgid: the new/current vfsgid of @inode + * + * Check wether @vfsgid is in the caller's group list or if the caller is + * privileged with CAP_FSETID over @inode. This can be used to determine + * whether the setgid bit can be kept or must be dropped. + * + * Return: true if the caller is sufficiently privileged, false if not. + */ +bool in_group_or_capable(struct user_namespace *mnt_userns, + const struct inode *inode, vfsgid_t vfsgid) +{ + if (vfsgid_in_group_p(vfsgid)) + return true; + if (capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FSETID)) + return true; + return false; +} + /** * mode_strip_sgid - handle the sgid bit for non-directories * @mnt_userns: User namespace of the mount the inode was created from @@ -2508,11 +2530,9 @@ umode_t mode_strip_sgid(struct user_namespace *mnt_userns, return mode; if (S_ISDIR(mode) || !dir || !(dir->i_mode & S_ISGID)) return mode; - if (in_group_p(i_gid_into_mnt(mnt_userns, dir))) - return mode; - if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID)) + if (in_group_or_capable(mnt_userns, dir, + i_gid_into_vfsgid(mnt_userns, dir))) return mode; - return mode & ~S_ISGID; } EXPORT_SYMBOL(mode_strip_sgid); diff --git a/fs/internal.h b/fs/internal.h index 6f0386b34fae..1de39bbc9ddd 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -151,6 +151,8 @@ extern int vfs_open(const struct path *, struct file *); */ extern long prune_icache_sb(struct super_block *sb, struct shrink_control *sc); extern int dentry_needs_remove_privs(struct dentry *dentry); +bool in_group_or_capable(struct user_namespace *mnt_userns, + const struct inode *inode, vfsgid_t vfsgid); /* * fs-writeback.c -- 2.34.1