Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932345AbbBYXqg (ORCPT ); Wed, 25 Feb 2015 18:46:36 -0500 Received: from mail-wg0-f46.google.com ([74.125.82.46]:33802 "EHLO mail-wg0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753843AbbBYXmU (ORCPT ); Wed, 25 Feb 2015 18:42:20 -0500 From: Andreas Gruenbacher X-Google-Original-From: Andreas Gruenbacher To: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org Subject: [RFC 09/21] richacl: Permission mapping functions Date: Thu, 26 Feb 2015 00:41:30 +0100 Message-Id: X-Mailer: git-send-email 2.1.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6461 Lines: 208 We need to map from POSIX permissions to NFSv4 permissions when a chmod() is done, from NFSv4 permissions to POSIX permissions when an acl is set (which implicitly sets the file permission bits), and from the MAY_READ/MAY_WRITE/MAY_EXEC/MAY_APPEND flags to NFSv4 permissions when doing an access check in a richacl. Signed-off-by: Andreas Gruenbacher --- fs/richacl_base.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 46 +++++++++++++++++++ 2 files changed, 163 insertions(+) diff --git a/fs/richacl_base.c b/fs/richacl_base.c index abf8bce..83731c7 100644 --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -55,3 +55,120 @@ richacl_clone(const struct richacl *acl) } return dup; } + +/** + * richacl_mask_to_mode - compute the file permission bits which correspond to @mask + * @mask: %ACE4_* permission mask + * + * See richacl_masks_to_mode(). + */ +static int +richacl_mask_to_mode(unsigned int mask) +{ + int mode = 0; + + if (mask & ACE4_POSIX_MODE_READ) + mode |= S_IROTH; + if (mask & ACE4_POSIX_MODE_WRITE) + mode |= S_IWOTH; + if (mask & ACE4_POSIX_MODE_EXEC) + mode |= S_IXOTH; + + return mode; +} + +/** + * richacl_masks_to_mode - compute the file permission bits from the file masks + * + * When setting a richacl, we set the file permission bits to indicate maximum + * permissions: for example, we set the Write permission when a mask contains + * ACE4_APPEND_DATA even if it does not also contain ACE4_WRITE_DATA. + * + * Permissions which are not in ACE4_POSIX_MODE_READ, ACE4_POSIX_MODE_WRITE, or + * ACE4_POSIX_MODE_EXEC cannot be represented in the file permission bits. + * Such permissions can still be effective, but not for new files or after a + * chmod(), and only if they were set explicitly, for example, by setting a + * richacl. + */ +int +richacl_masks_to_mode(const struct richacl *acl) +{ + return richacl_mask_to_mode(acl->a_owner_mask) << 6 | + richacl_mask_to_mode(acl->a_group_mask) << 3 | + richacl_mask_to_mode(acl->a_other_mask); +} +EXPORT_SYMBOL_GPL(richacl_masks_to_mode); + +/** + * richacl_mode_to_mask - compute a file mask from the lowest three mode bits + * + * When the file permission bits of a file are set with chmod(), this specifies + * the maximum permissions that processes will get. All permissions beyond + * that will be removed from the file masks, and become ineffective. + * + * We also add in the permissions which are always allowed no matter what the + * acl says. + */ +unsigned int +richacl_mode_to_mask(mode_t mode) +{ + unsigned int mask = ACE4_POSIX_ALWAYS_ALLOWED; + + if (mode & S_IROTH) + mask |= ACE4_POSIX_MODE_READ; + if (mode & S_IWOTH) + mask |= ACE4_POSIX_MODE_WRITE; + if (mode & S_IXOTH) + mask |= ACE4_POSIX_MODE_EXEC; + + return mask; +} + +/** + * richacl_want_to_mask - convert the iop->permission want argument to a mask + * @want: @want argument of the permission inode operation + * + * When checking for append, @want is (MAY_WRITE | MAY_APPEND). + * + * Richacls use the iop->may_create and iop->may_delete hooks which are + * used for checking if creating and deleting files is allowed. These hooks do + * not use richacl_want_to_mask(), so we do not have to deal with mapping + * MAY_WRITE to ACE4_ADD_FILE, ACE4_ADD_SUBDIRECTORY, and ACE4_DELETE_CHILD + * here. + */ +unsigned int +richacl_want_to_mask(unsigned int want) +{ + unsigned int mask = 0; + + if (want & MAY_READ) + mask |= ACE4_READ_DATA; + if (want & MAY_DELETE_SELF) + mask |= ACE4_DELETE; + if (want & MAY_TAKE_OWNERSHIP) + mask |= ACE4_WRITE_OWNER; + if (want & MAY_CHMOD) + mask |= ACE4_WRITE_ACL; + if (want & MAY_SET_TIMES) + mask |= ACE4_WRITE_ATTRIBUTES; + if (want & MAY_EXEC) + mask |= ACE4_EXECUTE; + /* + * differentiate MAY_WRITE from these request + */ + if (want & (MAY_APPEND | + MAY_CREATE_FILE | MAY_CREATE_DIR | + MAY_DELETE_CHILD)) { + if (want & MAY_APPEND) + mask |= ACE4_APPEND_DATA; + if (want & MAY_CREATE_FILE) + mask |= ACE4_ADD_FILE; + if (want & MAY_CREATE_DIR) + mask |= ACE4_ADD_SUBDIRECTORY; + if (want & MAY_DELETE_CHILD) + mask |= ACE4_DELETE_CHILD; + } else if (want & MAY_WRITE) + mask |= ACE4_WRITE_DATA; + return mask; +} +EXPORT_SYMBOL_GPL(richacl_want_to_mask); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index b16d865..41819f4 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -120,6 +120,49 @@ struct richacl { ACE4_WRITE_OWNER | \ ACE4_SYNCHRONIZE) +/* + * The POSIX permissions are supersets of the following NFSv4 permissions: + * + * - MAY_READ maps to READ_DATA or LIST_DIRECTORY, depending on the type + * of the file system object. + * + * - MAY_WRITE maps to WRITE_DATA or ACE4_APPEND_DATA for files, and to + * ADD_FILE, ACE4_ADD_SUBDIRECTORY, or ACE4_DELETE_CHILD for directories. + * + * - MAY_EXECUTE maps to ACE4_EXECUTE. + * + * (Some of these NFSv4 permissions have the same bit values.) + */ +#define ACE4_POSIX_MODE_READ ( \ + ACE4_READ_DATA | \ + ACE4_LIST_DIRECTORY) +#define ACE4_POSIX_MODE_WRITE ( \ + ACE4_WRITE_DATA | \ + ACE4_ADD_FILE | \ + ACE4_APPEND_DATA | \ + ACE4_ADD_SUBDIRECTORY | \ + ACE4_DELETE_CHILD) +#define ACE4_POSIX_MODE_EXEC ACE4_EXECUTE +#define ACE4_POSIX_MODE_ALL ( \ + ACE4_POSIX_MODE_READ | \ + ACE4_POSIX_MODE_WRITE | \ + ACE4_POSIX_MODE_EXEC) +/* + * These permissions are always allowed + * no matter what the acl says. + */ +#define ACE4_POSIX_ALWAYS_ALLOWED ( \ + ACE4_SYNCHRONIZE | \ + ACE4_READ_ATTRIBUTES | \ + ACE4_READ_ACL) +/* + * The owner is implicitly granted + * these permissions under POSIX. + */ +#define ACE4_POSIX_OWNER_ALLOWED ( \ + ACE4_WRITE_ATTRIBUTES | \ + ACE4_WRITE_OWNER | \ + ACE4_WRITE_ACL) /** * richacl_get - grab another reference to a richacl handle */ @@ -244,5 +287,8 @@ richace_is_same_identifier(const struct richace *a, const struct richace *b) } extern struct richacl *richacl_alloc(int); +extern int richacl_masks_to_mode(const struct richacl *); +extern unsigned int richacl_mode_to_mask(mode_t); +extern unsigned int richacl_want_to_mask(unsigned int); #endif /* __RICHACL_H */ -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/