Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1282413

[PATCH v16 14/22] richacl: Update the file masks in chmod()

Show all headers | View raw

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 <agruenba@redhat.com>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
---
 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 5826842..e4dd779 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+ * Return a copy of @acl where the file masks have been replaced by the file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 52c1595..e329826 100644
--- a/fs/richacl_inode.c
+++ b/fs/richacl_inode.c
@@ -224,3 +224,33 @@ 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 7bf912b6..a2d5600 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

--
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/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v16 00/22] Richacls (Core and Ext4) Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 01/22] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 09/22] richacl: Permission check algorithm Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 17/22] richacl: Automatic Inheritance Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 13/22] vfs: Cache richacl in struct inode Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 21/22] ext4: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 19/22] richacl: Add richacl xattr handler Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 04/22] vfs: Make the inode passed to inode_change_ok non-const Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 06/22] richacl: In-memory representation and helper functions Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 03/22] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 05/22] vfs: Add permission flags for setting file attributes Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 14/22] richacl: Update the file masks in chmod() Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 10/22] posix_acl: Unexport acl_by_type and make it static Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 22/22] ext4: Add richacl feature flag Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 07/22] richacl: Permission mapping functions Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:10 +0100
  [PATCH v16 12/22] vfs: Add get_richacl and set_richacl inode operations Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:20 +0100
  [PATCH v16 15/22] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-02 22:20 +0100
  Re: [PATCH v16 00/22] Richacls (Core and Ext4) Andreas Gruenbacher <agruenba@redhat.com> - 2015-12-03 23:20 +0100

csiph-web