From: Andreas Gruenbacher Date: Fri, 11 Jun 2010 16:12:47 +0530 Subject: [PATCH 05/16] richacl: Permission mapping functions Patch-mainline: not yet 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 Signed-off-by: Aneesh Kumar K.V --- fs/richacl_base.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/richacl.h | 27 +++++++++++++ 2 files changed, 125 insertions(+) --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -69,6 +69,104 @@ richacl_clone(const struct richacl *acl) } /** + * 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 |= MAY_READ; + if (mask & ACE4_POSIX_MODE_WRITE) + mode |= MAY_WRITE; + if (mask & ACE4_POSIX_MODE_EXEC) + mode |= MAY_EXEC; + + 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 & MAY_READ) + mask |= ACE4_POSIX_MODE_READ; + if (mode & MAY_WRITE) + mask |= ACE4_POSIX_MODE_WRITE; + if (mode & MAY_EXEC) + 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(int want) +{ + unsigned int mask = 0; + + if (want & MAY_READ) + mask |= ACE4_READ_DATA; + if (want & MAY_APPEND) + mask |= ACE4_APPEND_DATA; + else if (want & MAY_WRITE) + mask |= ACE4_WRITE_DATA; + if (want & MAY_EXEC) + mask |= ACE4_EXECUTE; + + return mask; +} +EXPORT_SYMBOL_GPL(richacl_want_to_mask); + +/** * richace_is_same_identifier - are both identifiers the same? */ int --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -111,6 +111,30 @@ 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 | \ @@ -241,5 +265,8 @@ extern struct richacl *richacl_alloc(int extern int richace_is_same_identifier(const struct richace *, const struct richace *); extern int richace_set_who(struct richace *, const char *); +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(int); #endif /* __RICHACL_H */