From patchwork Wed Nov 29 21:50:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Seth Forshee (DigitalOcean)" X-Patchwork-Id: 13473557 X-Patchwork-Delegate: paul@paul-moore.com Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8896361FC2; Wed, 29 Nov 2023 21:50:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kmCkgtjR" Received: by smtp.kernel.org (Postfix) with ESMTPS id 033B2C433BA; Wed, 29 Nov 2023 21:50:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701294658; bh=RKuTcbYgZvHVKggTHC2zuvdJ26QENxjmgCweIZ3eegk=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=kmCkgtjRpxDsMEC0ScFiG7Rywqww7dZDZdR+Pvl32kQYeYkBhGbMSQ5A15W+uVQAp zIU/dIEFszza21uQmGoWrZTNZOwdsKbhCNSWZEkfc/gNsaPlyBQiFbcyyQLvkIECRG O2tXZprWsHPVckIsbdUyITzR4EIteUYDgn4DqMFwCawFTVm3RDkU8Lr+sNYYhs2lCf JN0dIJ0OIL/kLZy3QYqigqL3elHHlVqRoeBjGiU3O/BUOZLcYzmLdWpTpFHGHg+hoF gPc/oBvA+YOpi1ZYy+wbesrPM9mwGAGCu1dsm217JRrW67zGDbe7G7UZdsMhJk9m+X /OfUFmXZuGZYg== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6CDEC10F04; Wed, 29 Nov 2023 21:50:57 +0000 (UTC) From: "Seth Forshee (DigitalOcean)" Date: Wed, 29 Nov 2023 15:50:28 -0600 Subject: [PATCH 10/16] fs: add vfs_remove_fscaps() Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20231129-idmap-fscap-refactor-v1-10-da5a26058a5b@kernel.org> References: <20231129-idmap-fscap-refactor-v1-0-da5a26058a5b@kernel.org> In-Reply-To: <20231129-idmap-fscap-refactor-v1-0-da5a26058a5b@kernel.org> To: Christian Brauner , Serge Hallyn , Paul Moore , Eric Paris , James Morris , Alexander Viro , Miklos Szeredi , Amir Goldstein Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, audit@vger.kernel.org, linux-unionfs@vger.kernel.org, "Seth Forshee (DigitalOcean)" X-Mailer: b4 0.12.4 X-Developer-Signature: v=1; a=openpgp-sha256; l=3668; i=sforshee@kernel.org; h=from:subject:message-id; bh=RKuTcbYgZvHVKggTHC2zuvdJ26QENxjmgCweIZ3eegk=; =?utf-8?q?b=3DowEBbQGS/pANAwAKAVMDma7l9DHJAcsmYgBlZ7I64UBhX2GGFexH+bBTTpHN+?= =?utf-8?q?1ZZSs/s9GteH5Ya_Ao5bAXqJATMEAAEKAB0WIQSQnt+rKAvnETy4Hc9TA5mu5fQxy?= =?utf-8?q?QUCZWeyOgAKCRBTA5mu5fQxyZvhB/_9/0OH7uhQCHOgqtW6u1AsBk1GTbo0kK20Cn?= =?utf-8?q?bD4KJ5wbBLk1DZBgcWkKnbOEwoDBTbsYps5A36R5VNO_+3Jq2pg5sBcXDPdXt43p2?= =?utf-8?q?/gfipt41G5bIASpTWS8pnm/RFRtLvNURjT8VLyGrEcrY9H85teLbZ2qyC_PHy7qr5?= =?utf-8?q?+BlZwhbvKU3JmBQSjSS4CAP2nzCOumOJGM3t2SeYGZK15fNVExtZSKfg+ueOdR9Bc?= =?utf-8?q?eWrP2U_3Vp+H5E9v+M/1Sl3vEwEAdBaicRWTe69HeZD0cn0is1XhMgEf3iu940R8R?= =?utf-8?q?LLSo97mWrtbmWNopBk91?= XzbOBlAStUH2Ld9boVsTifWqMzAAuI X-Developer-Key: i=sforshee@kernel.org; a=openpgp; fpr=2ABCA7498D83E1D32D51D3B5AB4800A62DB9F73A X-Endpoint-Received: by B4 Relay for sforshee@kernel.org/default with auth_id=103 Provide a type-safe interface for removing filesystem capabilities and a generic implementation suitable for most filesystems. Also add an internal interface, __vfs_remove_fscaps(), which is called with the inode lock held and skips security checks for later use from the capability code. Signed-off-by: Seth Forshee (DigitalOcean) --- fs/xattr.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 2 ++ 2 files changed, 79 insertions(+) diff --git a/fs/xattr.c b/fs/xattr.c index 03cc824e4f87..f60ef2a79dfa 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -334,6 +334,83 @@ int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, } EXPORT_SYMBOL(vfs_set_fscaps); +static int generic_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry) +{ + return __vfs_removexattr(idmap, dentry, XATTR_NAME_CAPS); +} + +/** + * __vfs_remove_fscaps - remove filesystem capabilities without security checks + * @idmap: idmap of the mount the inode was found from + * @dentry: the dentry from which to remove filesystem capabilities + * + * This function removes any filesystem capabilities from the specified + * dentry. Does not perform any security checks, and callers must hold the + * inode lock. + * + * Return: 0 on success, a negative errno on error. + */ +int __vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry) +{ + struct inode *inode = dentry->d_inode; + int error; + + if (inode->i_op->remove_fscaps) + error = inode->i_op->remove_fscaps(idmap, dentry); + else + error = generic_remove_fscaps(idmap, dentry); + + return error; +} + +/** + * vfs_remove_fscaps - remove filesystem capabilities + * @idmap: idmap of the mount the inode was found from + * @dentry: the dentry from which to remove filesystem capabilities + * + * This function removes any filesystem capabilities from the specified + * dentry. + * + * Return: 0 on success, a negative errno on error. + */ +int vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry) +{ + struct inode *inode = dentry->d_inode; + struct inode *delegated_inode = NULL; + int error; + +retry_deleg: + inode_lock(inode); + + error = xattr_permission(idmap, inode, XATTR_NAME_CAPS, MAY_WRITE); + if (error) + goto out_inode_unlock; + + error = security_inode_removexattr(idmap, dentry, XATTR_NAME_CAPS); + if (error) + goto out_inode_unlock; + + error = try_break_deleg(inode, &delegated_inode); + if (error) + goto out_inode_unlock; + + error = __vfs_remove_fscaps(idmap, dentry); + if (!error) + fsnotify_xattr(dentry); + +out_inode_unlock: + inode_unlock(inode); + + if (delegated_inode) { + error = break_deleg_wait(&delegated_inode); + if (!error) + goto retry_deleg; + } + + return error; +} +EXPORT_SYMBOL(vfs_remove_fscaps); + int __vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, struct inode *inode, const char *name, const void *value, diff --git a/include/linux/fs.h b/include/linux/fs.h index 80992e210b83..057bad11a4e6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2061,6 +2061,8 @@ extern int vfs_get_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, struct vfs_caps *caps); extern int vfs_set_fscaps(struct mnt_idmap *idmap, struct dentry *dentry, const struct vfs_caps *caps, int flags); +extern int __vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry); +extern int vfs_remove_fscaps(struct mnt_idmap *idmap, struct dentry *dentry); enum freeze_holder { FREEZE_HOLDER_KERNEL = (1U << 0),