From: Andreas Gruenbacher Date: Fri, 11 Jun 2010 16:12:52 +0530 Subject: [PATCH 12/16] richacl: Automatic Inheritance Patch-mainline: not yet Automatic Inheritance (AI) allows changes to the acl of a directory to recursively propagate down to files and directories in the directory. To implement this, the kernel keeps track of which permissions have been inherited, and makes sure that permission propagation is turned off when the file permission bits of a file are changed (upon create or chmod). The actual permission propagation is implemented in user space. AI works as follows: - When the ACL4_AUTO_INHERIT flag in the acl of a file is cleared, the file is not affected by AI. - When the ACL4_AUTO_INHERIT flag in the acl of a directory is set and a file or subdirectory is created in that directory, files created in the directory will have the ACL4_AUTO_INHERIT flag set, and all inherited aces will have the ACE4_INHERITED_ACE flag set. This allows user space to distinguish between aces which have been inherited, and aces which have been explicitly added. - When the ACL4_PROTECTED acl flag in the acl of a file is set, AI will not modify the acl of the file. This does not affect propagation of permissions from the file to its children (if the file is a directory). Linux does not have a way of creating files without setting the file permission bits, so all files created inside a directory with ACL4_AUTO_INHERIT set will also have the ACL4_PROTECTED flag set. This effectively disables AI. Protocols which support creating files without specifying permissions can explicitly clear the ACL4_PROTECTED flag after creating a file (and reset the file masks to "undo" applying the create mode; see richacl_compute_max_masks()). This is a workaround; a per-create or per-process flag indicating to ignore the create mode when AI is in effect would fix this problem. Signed-off-by: Andreas Gruenbacher Signed-off-by: Aneesh Kumar K.V --- fs/richacl_base.c | 15 ++++++++++++++- include/linux/richacl.h | 25 ++++++++++++++++++++++++- 2 files changed, 38 insertions(+), 2 deletions(-) --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -352,7 +352,8 @@ richacl_chmod(struct richacl *acl, mode_ if (acl->a_owner_mask == owner_mask && acl->a_group_mask == group_mask && - acl->a_other_mask == other_mask) + acl->a_other_mask == other_mask && + (!richacl_is_auto_inherit(acl) || richacl_is_protected(acl))) return acl; clone = richacl_clone(acl); @@ -363,6 +364,8 @@ richacl_chmod(struct richacl *acl, mode_ clone->a_owner_mask = owner_mask; clone->a_group_mask = group_mask; clone->a_other_mask = other_mask; + if (richacl_is_auto_inherit(clone)) + clone->a_flags |= ACL4_PROTECTED; return clone; } @@ -539,6 +542,16 @@ richacl_inherit(const struct richacl *di acl->a_other_mask &= richacl_mode_to_mask(inode->i_mode); mask = ~S_IRWXUGO | richacl_masks_to_mode(acl); + if (richacl_is_auto_inherit(dir_acl)) { + /* + * We need to set ACL4_PROTECTED because we are + * doing an implicit chmod + */ + acl->a_flags = ACL4_AUTO_INHERIT | ACL4_PROTECTED; + richacl_for_each_entry(ace, acl) + ace->e_flags |= ACE4_INHERITED_ACE; + } + mask: inode->i_mode &= mask; return acl; --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -47,6 +47,15 @@ struct richacl { _ace != _acl->a_entries - 1; \ _ace--) +/* a_flags values */ +#define ACL4_AUTO_INHERIT 0x01 +#define ACL4_PROTECTED 0x02 +/*#define ACL4_DEFAULTED 0x04*/ + +#define ACL4_VALID_FLAGS ( \ + ACL4_AUTO_INHERIT | \ + ACL4_PROTECTED) + /* e_type values */ #define ACE4_ACCESS_ALLOWED_ACE_TYPE 0x0000 #define ACE4_ACCESS_DENIED_ACE_TYPE 0x0001 @@ -61,6 +70,7 @@ struct richacl { /*#define ACE4_SUCCESSFUL_ACCESS_ACE_FLAG 0x0010*/ /*#define ACE4_FAILED_ACCESS_ACE_FLAG 0x0020*/ #define ACE4_IDENTIFIER_GROUP 0x0040 +#define ACE4_INHERITED_ACE 0x0080 /* in-memory representation only */ #define ACE4_SPECIAL_WHO 0x4000 @@ -69,7 +79,8 @@ struct richacl { ACE4_DIRECTORY_INHERIT_ACE | \ ACE4_NO_PROPAGATE_INHERIT_ACE | \ ACE4_INHERIT_ONLY_ACE | \ - ACE4_IDENTIFIER_GROUP) + ACE4_IDENTIFIER_GROUP | \ + ACE4_INHERITED_ACE) /* e_mask bitflags */ #define ACE4_READ_DATA 0x00000001 @@ -162,6 +173,18 @@ richacl_put(struct richacl *acl) kfree(acl); } +static inline int +richacl_is_auto_inherit(const struct richacl *acl) +{ + return acl->a_flags & ACL4_AUTO_INHERIT; +} + +static inline int +richacl_is_protected(const struct richacl *acl) +{ + return acl->a_flags & ACL4_PROTECTED; +} + /* * Special e_who identifiers: we use these pointer values in comparisons * instead of doing a strcmp.