Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:38626 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932340AbbKCPTG (ORCPT ); Tue, 3 Nov 2015 10:19:06 -0500 From: Andreas Gruenbacher To: Alexander Viro , "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 Cc: Andreas Gruenbacher Subject: [PATCH v13 13/51] richacl: Update the file masks in chmod() Date: Tue, 3 Nov 2015 16:16:49 +0100 Message-Id: <1446563847-14005-14-git-send-email-agruenba@redhat.com> In-Reply-To: <1446563847-14005-1-git-send-email-agruenba@redhat.com> References: <1446563847-14005-1-git-send-email-agruenba@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 --- fs/richacl_base.c | 42 ++++++++++++++++++++++++++++++++++++++++++ fs/richacl_inode.c | 30 ++++++++++++++++++++++++++++++ include/linux/richacl.h | 2 ++ 3 files changed, 74 insertions(+) diff --git a/fs/richacl_base.c b/fs/richacl_base.c index d0ab5e9..00e87be 100644 --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -340,3 +340,45 @@ restart: 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+ * @mode: new file permission bits including the file type + * + * Return a copy of @acl where the file masks have been replaced by the file + * masks corresponding to the file permission bits in @mode, or returns @acl + * itself if the file masks are already up to date.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. + */ +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; +} +EXPORT_SYMBOL_GPL(__richacl_chmod); diff --git a/fs/richacl_inode.c b/fs/richacl_inode.c index c41a6c4..301f246 100644 --- a/fs/richacl_inode.c +++ b/fs/richacl_inode.c @@ -222,3 +222,33 @@ out: return denied ? -EACCES : 0; } EXPORT_SYMBOL_GPL(richacl_permission); + +/** + * 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 de7d0d9..3626314 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -184,8 +184,10 @@ extern int richacl_masks_to_mode(const struct richacl *); extern unsigned int richacl_mode_to_mask(umode_t); extern unsigned int richacl_want_to_mask(unsigned int); extern void richacl_compute_max_masks(struct richacl *); +extern struct richacl *__richacl_chmod(struct richacl *, umode_t); /* richacl_inode.c */ extern int richacl_permission(struct inode *, const struct richacl *, int); +extern int richacl_chmod(struct inode *, umode_t); #endif /* __RICHACL_H */ -- 2.5.0