Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754056AbcJKMwW (ORCPT ); Tue, 11 Oct 2016 08:52:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46912 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751672AbcJKMwP (ORCPT ); Tue, 11 Oct 2016 08:52:15 -0400 From: Andreas Gruenbacher To: Alexander Viro Cc: Andreas Gruenbacher , Christoph Hellwig , "Theodore Ts'o" , Andreas Dilger , "J. Bruce Fields" , Jeff Layton , Trond Myklebust , Anna Schumaker , Dave Chinner , linux-ext4@vger.kernel.org, xfs@oss.sgi.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-api@vger.kernel.org Subject: [PATCH v27 12/21] richacl: Update the file masks in chmod() Date: Tue, 11 Oct 2016 14:50:47 +0200 Message-Id: <1476190256-1677-13-git-send-email-agruenba@redhat.com> In-Reply-To: <1476190256-1677-1-git-send-email-agruenba@redhat.com> References: <1476190256-1677-1-git-send-email-agruenba@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 11 Oct 2016 12:52:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3922 Lines: 115 Doing a chmod() sets the file mode, which includes the file permission bits. When a file has a richacl, the permissions that the richacl grants need to be limited to what the new file permission bits allow. This is done by setting the file masks in the richacl to what the file permission bits map to. The richacl access check algorithm takes the file masks into account, which ensures that the richacl cannot grant too many permissions. It is possible to explicitly add permissions to the file masks which go beyond what the file permission bits can grant (like the RICHACE_WRITE_ACL permission). The POSIX.1 standard calls this an alternate file access control mechanism. A subsequent chmod() would ensure that those permissions are disabled again. Signed-off-by: Andreas Gruenbacher Reviewed-by: J. Bruce Fields Acked-by: Jeff Layton --- fs/richacl.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 1 + 2 files changed, 72 insertions(+) diff --git a/fs/richacl.c b/fs/richacl.c index 731c468..a199245 100644 --- a/fs/richacl.c +++ b/fs/richacl.c @@ -541,3 +541,74 @@ void richacl_compute_max_masks(struct richacl *acl) acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED); } EXPORT_SYMBOL_GPL(richacl_compute_max_masks); + +/** + * __richacl_chmod - update the file masks to reflect the new mode + * @acl: access control list + * @mode: new file permission bits including the file type + * + * Return a copy of @acl where the file masks have been replaced by the file + * masks corresponding to the file permission bits in @mode, or returns @acl + * itself if the file masks are already up to date. Takes over a reference + * to @acl. + */ +static struct richacl * +__richacl_chmod(struct richacl *acl, umode_t mode) +{ + unsigned int x = S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD; + unsigned int owner_mask, group_mask, other_mask; + struct richacl *clone; + + owner_mask = richacl_mode_to_mask(mode >> 6) & ~x; + group_mask = richacl_mode_to_mask(mode >> 3) & ~x; + other_mask = richacl_mode_to_mask(mode) & ~x; + + if (acl->a_owner_mask == owner_mask && + acl->a_group_mask == group_mask && + acl->a_other_mask == other_mask && + (acl->a_flags & RICHACL_MASKED) && + (acl->a_flags & RICHACL_WRITE_THROUGH)) + return acl; + + clone = richacl_clone(acl, GFP_KERNEL); + richacl_put(acl); + if (!clone) + return ERR_PTR(-ENOMEM); + + clone->a_flags |= (RICHACL_WRITE_THROUGH | RICHACL_MASKED); + clone->a_owner_mask = owner_mask; + clone->a_group_mask = group_mask; + clone->a_other_mask = other_mask; + + return clone; +} + +/** + * richacl_chmod - filesystem chmod helper + * @inode: inode whose file permission bits to change + * @mode: new file permission bits including the file type + * + * Helper for filesystems to use to perform a chmod on the richacl of an inode. + */ +int +richacl_chmod(struct inode *inode, umode_t mode) +{ + struct richacl *acl; + int retval; + + if (S_ISLNK(mode)) + return -EOPNOTSUPP; + if (!inode->i_op->set_richacl) + return -EOPNOTSUPP; + acl = get_richacl(inode); + if (IS_ERR_OR_NULL(acl)) + return PTR_ERR(acl); + acl = __richacl_chmod(acl, mode); + if (IS_ERR(acl)) + return PTR_ERR(acl); + retval = inode->i_op->set_richacl(inode, acl); + richacl_put(acl); + + return retval; +} +EXPORT_SYMBOL(richacl_chmod); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index 207fe06..3cd5e53 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -189,5 +189,6 @@ extern int richacl_masks_to_mode(const struct richacl *); extern unsigned int richacl_mode_to_mask(umode_t); extern int richacl_permission(struct inode *, const struct richacl *, int); extern void richacl_compute_max_masks(struct richacl *); +extern int richacl_chmod(struct inode *, umode_t); #endif /* __RICHACL_H */ -- 2.7.4