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[PATCH v10 13/46] richacl: Update the file masks in chmod()

From Andreas Gruenbacher <andreas.gruenbacher@gmail.com>
Newsgroups linux.kernel
Subject [PATCH v10 13/46] richacl: Update the file masks in chmod()
Date 2015-10-12 01:10 +0200
Message-ID <qixUD-61y-43@gated-at.bofh.it> (permalink)
References <qixKV-5z8-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: Andreas Gruenbacher <agruenba@redhat.com>

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 78e81df..764d73a 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+ * Return a copy of @acl where the file masks have been replaced by the file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 c0458db..be11832 100644
--- a/fs/richacl_inode.c
+++ b/fs/richacl_inode.c
@@ -222,3 +222,33 @@ 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 3f9dd10..152000c 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -303,8 +303,10 @@ 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

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[PATCH v10 00/46] Richacls Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:00 +0200
  [PATCH v10 37/46] nfsd: Add support for the MAY_CREATE_{FILE,DIR} permissions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 35/46] nfsd: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 27/46] richacl: Propagate everyone@ permissions to other aces Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 17/46] richacl: xattr mapping functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 23/46] xfs: Make xfs_set_mode non-static Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
    Re: [PATCH v10 23/46] xfs: Make xfs_set_mode non-static Dave Chinner <david@fromorbit.com> - 2015-10-12 01:50 +0200
  [PATCH v10 43/46] nfs: Remove unused xdr page offsets in getacl/setacl arguments Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 24/46] xfs: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
    Re: [PATCH v10 24/46] xfs: Add richacl support Dave Chinner <david@fromorbit.com> - 2015-10-12 02:20 +0200
      Re: [PATCH v10 24/46] xfs: Add richacl support Andreas Grünbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 04:00 +0200
        Re: [PATCH v10 24/46] xfs: Add richacl support Dave Chinner <david@fromorbit.com> - 2015-10-12 06:10 +0200
          Re: [PATCH v10 24/46] xfs: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-12 08:00 +0200
            Re: [PATCH v10 24/46] xfs: Add richacl support Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-10-13 21:30 +0200
          Re: [PATCH v10 24/46] xfs: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-13 15:40 +0200
  [PATCH v10 28/46] richacl: Set the owner permissions to the owner mask Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 30/46] richacl: Isolate the owner and group classes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 19/46] vfs: Add richacl permission checking Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 26/46] richacl: Move everyone@ aces down the acl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 18/46] richacl: Add richacl xattr handler Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 42/46] nfs: Fix GETATTR bitmap verification Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 36/46] nfsd: Add support for the v4.1 dacl attribute Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 13/46] richacl: Update the file masks in chmod() Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 32/46] richacl: Create richacl from mode values Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 22/46] xfs: Fix error path in xfs_get_acl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 20/46] ext4: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 11/46] vfs: Add get_richacl and set_richacl inode operations Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 14/46] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 33/46] nfsd: Keep list of acls to dispose of in compoundargs Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 38/46] richacl: Add support for unmapped identifiers Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
    Re: [PATCH v10 38/46] richacl: Add support for unmapped identifiers Dave Chinner <david@fromorbit.com> - 2015-10-12 02:30 +0200
      Re: [PATCH v10 38/46] richacl: Add support for unmapped identifiers Andreas Grünbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 04:00 +0200
  [PATCH v10 29/46] richacl: Set the other permissions to the other mask Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 45/46] nfs: Add support for the v4.1 dacl attribute Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 41/46] sunrpc: Add xdr_init_encode_pages Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 46/46] richacl: uapi header split Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 44/46] nfs: Add richacl support Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
    Re: [PATCH v10 44/46] nfs: Add richacl support Anna Schumaker <Anna.Schumaker@netapp.com> - 2015-10-12 16:40 +0200
      Re: [PATCH v10 44/46] nfs: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-12 21:50 +0200
  [PATCH v10 21/46] ext4: Add richacl feature flag Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 25/46] richacl: acl editing helper functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 15/46] richacl: Create-time inheritance Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 31/46] richacl: Apply the file masks to a richacl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:10 +0200
  [PATCH v10 40/46] sunrpc: Allow to demand-allocate pages to encode into Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:20 +0200
  [PATCH v10 39/46] ext4: Don't allow unmapped identifiers in richacls Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:20 +0200
  [PATCH v10 34/46] nfsd: Use richacls as internal acl representation Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:20 +0200
  [PATCH v10 16/46] richacl: Automatic Inheritance Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:30 +0200
  [PATCH v10 03/46] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 12/46] vfs: Cache richacl in struct inode Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 09/46] richacl: Permission check algorithm Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 10/46] vfs: Cache base_acl objects in inodes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 08/46] richacl: Compute maximum file masks from an acl Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 04/46] vfs: Make the inode passed to inode_change_ok non-const Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 05/46] vfs: Add permission flags for setting file attributes Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 02/46] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:40 +0200
  [PATCH v10 01/46] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:50 +0200
  [PATCH v10 07/46] richacl: Permission mapping functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:50 +0200
  [PATCH v10 06/46] richacl: In-memory representation and helper functions Andreas Gruenbacher <andreas.gruenbacher@gmail.com> - 2015-10-12 01:50 +0200

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