[PATCH v11 32/48] richacl: Create richacl from mode values

Andreas Gruenbacher
2015-10-16T15:22:08Z

A file can have "no acl" in the sense that only the file mode permission
bits determine access. In that case, the getxattr system call fails with
errno == ENODATA (No such attribute).

Over the NFSv4 protocol, a file always has an acl, and we convert the file
mode permission bits into an equivalent acl with richacl_from_mode. Such
"trivial" acls can be converted back to a file mode with
richacl_equiv_mode.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
---
fs/richacl_compat.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/richacl.h | 1 +
2 files changed, 89 insertions(+)

diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
index c99274f..e513958 100644
--- a/fs/richacl_compat.c
+++ b/fs/richacl_compat.c
@@ -827,3 +827,91 @@ richacl_apply_masks(struct richacl **acl, kuid_t owner)
return 0;
}
EXPORT_SYMBOL_GPL(richacl_apply_masks);
+
+/**
+ * richacl_from_mode - create an acl which corresponds to @mode
+ *
+ * The resulting acl doesn't have the RICHACL_MASKED flag set.
+ *
+ * @mode: file mode including the file type
+ */
+struct richacl *
+richacl_from_mode(umode_t mode)
+{
+ unsigned int owner_mask = richacl_mode_to_mask(mode >> 6);
+ unsigned int group_mask = richacl_mode_to_mask(mode >> 3);
+ unsigned int other_mask = richacl_mode_to_mask(mode);
+ unsigned int denied;
+ unsigned int entries = 0;
+ struct richacl *acl;
+ struct richace *ace;
+
+ /* RICHACE_DELETE_CHILD is meaningless for non-directories. */
+ if (!S_ISDIR(mode)) {
+ owner_mask &= ~RICHACE_DELETE_CHILD;
+ group_mask &= ~RICHACE_DELETE_CHILD;
+ other_mask &= ~RICHACE_DELETE_CHILD;
+ }
+
+ denied = ~owner_mask & (group_mask | other_mask);
+ if (denied)
+ entries++; /* owner@ deny entry needed */
+ if (owner_mask & ~(group_mask & other_mask))
+ entries++; /* owner@ allow entry needed */
+ denied = ~group_mask & other_mask;
+ if (denied)
+ entries++; /* group@ deny entry needed */
+ if (group_mask & ~other_mask)
+ entries++; /* group@ allow entry needed */
+ if (other_mask)
+ entries++; /* everyone@ allow entry needed */
+
+ acl = richacl_alloc(entries, GFP_KERNEL);
+ if (!acl)
+ return NULL;
+ acl->a_owner_mask = owner_mask;
+ acl->a_group_mask = group_mask;
+ acl->a_other_mask = other_mask;
+ ace = acl->a_entries;
+
+ denied = ~owner_mask & (group_mask | other_mask);
+ if (denied) {
+ ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
+ ace->e_flags = RICHACE_SPECIAL_WHO;
+ ace->e_mask = denied;
+ ace->e_id.special = RICHACE_OWNER_SPECIAL_ID;
+ ace++;
+ }
+ if (owner_mask & ~(group_mask & other_mask)) {
+ ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
+ ace->e_flags = RICHACE_SPECIAL_WHO;
+ ace->e_mask = owner_mask;
+ ace->e_id.special = RICHACE_OWNER_SPECIAL_ID;
+ ace++;
+ }
+ denied = ~group_mask & other_mask;
+ if (denied) {
+ ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
+ ace->e_flags = RICHACE_SPECIAL_WHO;
+ ace->e_mask = denied;
+ ace->e_id.special = RICHACE_GROUP_SPECIAL_ID;
+ ace++;
+ }
+ if (group_mask & ~other_mask) {
+ ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
+ ace->e_flags = RICHACE_SPECIAL_WHO;
+ ace->e_mask = group_mask;
+ ace->e_id.special = RICHACE_GROUP_SPECIAL_ID;
+ ace++;
+ }
+ if (other_mask) {
+ ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
+ ace->e_flags = RICHACE_SPECIAL_WHO;
+ ace->e_mask = other_mask;
+ ace->e_id.special = RICHACE_EVERYONE_SPECIAL_ID;
+ ace++;
+ }
+
+ return acl;
+}
+EXPORT_SYMBOL_GPL(richacl_from_mode);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index 3f3445b..6d2e5bd 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -249,5 +249,6 @@ extern struct richacl *richacl_create(umode_t *, struct inode *);

/* richacl_compat.c */
extern int richacl_apply_masks(struct richacl **, kuid_t);
+extern struct richacl *richacl_from_mode(umode_t);

#endif /* __RICHACL_H */