From patchwork Tue Jul 27 10:48:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 12402447 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C3AFC4338F for ; Tue, 27 Jul 2021 10:50:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56F75611C5 for ; Tue, 27 Jul 2021 10:50:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236379AbhG0Kua (ORCPT ); Tue, 27 Jul 2021 06:50:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:55674 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236169AbhG0Ku3 (ORCPT ); Tue, 27 Jul 2021 06:50:29 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id B218E6135A; Tue, 27 Jul 2021 10:50:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627383029; bh=DXeBxntle03LxjR/sp5v3vkSocLKm4g6taMWkMmXodk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=X7HJVWbvk0tBSl8ovUoqxoyqWSPboLkyGdhI4Lc7vI6ktormTVwmUu3HmUdrLJClB F1NoaV1K4m4hsQqCvMCjHQ2grR/lxzo09v0OA8P3wFWmhOqgrkNDcd/eCpu1TbDoYm OGA7XwY/Qm1yLjhg8h7yr0VRkp0G02d4n8yNW5heFOmB6R890hqLTkBeYJsEnqm3D0 O5Wf39IYzjJagm+U4kiFP53Xnyb5x+fqFTVYEstF1zcgNGfIQQvGHKQZobHZqQkh+Q gi+mLtZtIyjf5lPDroTbyrtZd79KR1WSHm5N2eE4JGyiiJQRH41bmq4dwhhtv9aC3X OTSRmELwyRluA== From: Christian Brauner To: Christoph Hellwig , Chris Mason , Josef Bacik , David Sterba Cc: Al Viro , linux-btrfs@vger.kernel.org, Christian Brauner , Christoph Hellwig , Matthew Wilcox , linux-fsdevel@vger.kernel.org Subject: [PATCH v4 01/21] namei: add mapping aware lookup helper Date: Tue, 27 Jul 2021 12:48:40 +0200 Message-Id: <20210727104900.829215-2-brauner@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210727104900.829215-1-brauner@kernel.org> References: <20210727104900.829215-1-brauner@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5026; h=from:subject; bh=oa4AcwY1bGhWgVrnncnHqGiwwPocGdhs0DBLxErCIjY=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMST8fzJRhpvrbeTEu9HZE7WLzV03Hw/pWTz1qLmlwcfCiINb Z7kxdpSyMIhxMciKKbI4tJuEyy3nqdhslKkBM4eVCWQIAxenAExENpSRYePHRX99a1Nm+gV729smBd lfrpiocebn9E5HlalzTdIOXGNk+Jbffbfktv/Bzesk/77tO3tRO7N+ywdHUYGfrzXfqv8tYgAA X-Developer-Key: i=christian.brauner@ubuntu.com; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Christian Brauner Various filesystems rely on the lookup_one_len() helper to lookup a single path component relative to a well-known starting point. Allow such filesystems to support idmapped mounts by adding a version of this helper to take the idmap into account when calling inode_permission(). This change is a required to let btrfs (and other filesystems) support idmapped mounts. Cc: Christoph Hellwig Cc: Al Viro Cc: Matthew Wilcox (Oracle) Cc: linux-fsdevel@vger.kernel.org Reviewed-by: Josef Bacik Signed-off-by: Christian Brauner Reviewed-by: Christoph Hellwig --- /* v2 */ - Al Viro : - Add a new lookup helper instead of changing the old ones. /* v3 */ unchanged /* v4 */ - Christoph Hellwig , Matthew Wilcox (Oracle) : - Simplify the name of lookup_mapped_one_len() to either lookup_one_mapped() or lookup_one(). The *_len() prefix in all those helper apparently just exists for historical reasons because we used to have lookup_dentry(), then grew lookup_one(), and then grew lookup_one_len(). --- fs/namei.c | 43 +++++++++++++++++++++++++++++++++++++------ include/linux/namei.h | 2 ++ 2 files changed, 39 insertions(+), 6 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index bf6d8a738c59..902df46e7dd3 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2575,8 +2575,9 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, } EXPORT_SYMBOL(vfs_path_lookup); -static int lookup_one_len_common(const char *name, struct dentry *base, - int len, struct qstr *this) +static int lookup_one_common(struct user_namespace *mnt_userns, + const char *name, struct dentry *base, int len, + struct qstr *this) { this->name = name; this->len = len; @@ -2604,7 +2605,7 @@ static int lookup_one_len_common(const char *name, struct dentry *base, return err; } - return inode_permission(&init_user_ns, base->d_inode, MAY_EXEC); + return inode_permission(mnt_userns, base->d_inode, MAY_EXEC); } /** @@ -2628,7 +2629,7 @@ struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len WARN_ON_ONCE(!inode_is_locked(base->d_inode)); - err = lookup_one_len_common(name, base, len, &this); + err = lookup_one_common(&init_user_ns, name, base, len, &this); if (err) return ERR_PTR(err); @@ -2655,7 +2656,7 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) WARN_ON_ONCE(!inode_is_locked(base->d_inode)); - err = lookup_one_len_common(name, base, len, &this); + err = lookup_one_common(&init_user_ns, name, base, len, &this); if (err) return ERR_PTR(err); @@ -2664,6 +2665,36 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) } EXPORT_SYMBOL(lookup_one_len); +/** + * lookup_one - filesystem helper to lookup single pathname component + * @mnt_userns: user namespace of the mount the lookup is performed from + * @name: pathname component to lookup + * @base: base directory to lookup from + * @len: maximum length @len should be interpreted to + * + * Note that this routine is purely a helper for filesystem usage and should + * not be called by generic code. + * + * The caller must hold base->i_mutex. + */ +struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name, + struct dentry *base, int len) +{ + struct dentry *dentry; + struct qstr this; + int err; + + WARN_ON_ONCE(!inode_is_locked(base->d_inode)); + + err = lookup_one_common(mnt_userns, name, base, len, &this); + if (err) + return ERR_PTR(err); + + dentry = lookup_dcache(&this, base, 0); + return dentry ? dentry : __lookup_slow(&this, base, 0); +} +EXPORT_SYMBOL(lookup_one); + /** * lookup_one_len_unlocked - filesystem helper to lookup single pathname component * @name: pathname component to lookup @@ -2683,7 +2714,7 @@ struct dentry *lookup_one_len_unlocked(const char *name, int err; struct dentry *ret; - err = lookup_one_len_common(name, base, len, &this); + err = lookup_one_common(&init_user_ns, name, base, len, &this); if (err) return ERR_PTR(err); diff --git a/include/linux/namei.h b/include/linux/namei.h index be9a2b349ca7..df106b6d3cc5 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -68,6 +68,8 @@ extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int); extern struct dentry *lookup_one_len(const char *, struct dentry *, int); extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int); extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int); +extern struct dentry *lookup_one(struct user_namespace *, const char *, + struct dentry *, int); extern int follow_down_one(struct path *); extern int follow_down(struct path *);