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Groups > linux.kernel > #1463688

[PATCH v25 14/22] richacl: Check if an acl is equivalent to a file mode

From Andreas Gruenbacher <agruenba@redhat.com>
Newsgroups linux.kernel
Subject [PATCH v25 14/22] richacl: Check if an acl is equivalent to a file mode
Date 2016-08-16 13:10 +0200
Message-ID <s6KpP-2jv-1@gated-at.bofh.it> (permalink)
References <s6KpP-2jv-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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ACLs are considered equivalent to file modes if they only consist of
owner@, group@, and everyone@ entries, the owner@ permissions do not
depend on whether the owner is a member in the owning group, and no
inheritance flags are set.  This test is used to avoid storing richacls
if the acl can be computed from the file permission bits.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
---
 fs/richacl.c            | 104 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/richacl.h |   1 +
 2 files changed, 105 insertions(+)

diff --git a/fs/richacl.c b/fs/richacl.c
index a199245..1022983 100644
--- a/fs/richacl.c
+++ b/fs/richacl.c
@@ -612,3 +612,107 @@ richacl_chmod(struct inode *inode, umode_t mode)
 	return retval;
 }
 EXPORT_SYMBOL(richacl_chmod);
+
+/**
+ * richacl_equiv_mode  -  compute the mode equivalent of @acl
+ *
+ * An acl is considered equivalent to a file mode if it only consists of
+ * owner@, group@, and everyone@ entries and the owner@ permissions do not
+ * depend on whether the owner is a member in the owning group.
+ */
+int
+richacl_equiv_mode(const struct richacl *acl, umode_t *mode_p)
+{
+	umode_t mode = *mode_p;
+
+	/*
+	 * The RICHACE_DELETE_CHILD flag is meaningless for non-directories, so
+	 * we ignore it.
+	 */
+	unsigned int x = S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD;
+	struct {
+		unsigned int allowed;
+		unsigned int defined;  /* allowed or denied */
+	} owner = {
+		.defined = RICHACE_POSIX_ALWAYS_ALLOWED |
+			   RICHACE_POSIX_OWNER_ALLOWED  | x,
+	}, group = {
+		.defined = RICHACE_POSIX_ALWAYS_ALLOWED | x,
+	}, everyone = {
+		.defined = RICHACE_POSIX_ALWAYS_ALLOWED | x,
+	};
+	const struct richace *ace;
+
+	if (acl->a_flags & ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED))
+		return -1;
+
+	richacl_for_each_entry(ace, acl) {
+		if (ace->e_flags & ~RICHACE_SPECIAL_WHO)
+			return -1;
+
+		if (richace_is_owner(ace) || richace_is_everyone(ace)) {
+			x = ace->e_mask & ~owner.defined;
+			if (richace_is_allow(ace)) {
+				unsigned int group_denied =
+					group.defined & ~group.allowed;
+
+				if (x & group_denied)
+					return -1;
+				owner.allowed |= x;
+			} else /* if (richace_is_deny(ace)) */ {
+				if (x & group.allowed)
+					return -1;
+			}
+			owner.defined |= x;
+
+			if (richace_is_everyone(ace)) {
+				x = ace->e_mask;
+				if (richace_is_allow(ace)) {
+					group.allowed |=
+						x & ~group.defined;
+					everyone.allowed |=
+						x & ~everyone.defined;
+				}
+				group.defined |= x;
+				everyone.defined |= x;
+			}
+		} else if (richace_is_group(ace)) {
+			x = ace->e_mask & ~group.defined;
+			if (richace_is_allow(ace))
+				group.allowed |= x;
+			group.defined |= x;
+		} else
+			return -1;
+	}
+
+	if (group.allowed & ~owner.defined)
+		return -1;
+
+	if (acl->a_flags & RICHACL_MASKED) {
+		if (acl->a_flags & RICHACL_WRITE_THROUGH) {
+			owner.allowed = acl->a_owner_mask;
+			everyone.allowed = acl->a_other_mask;
+		} else {
+			owner.allowed &= acl->a_owner_mask;
+			everyone.allowed &= acl->a_other_mask;
+		}
+		group.allowed &= acl->a_group_mask;
+	}
+
+	mode = (mode & ~S_IRWXUGO) |
+	       (richacl_mask_to_mode(owner.allowed) << 6) |
+	       (richacl_mask_to_mode(group.allowed) << 3) |
+		richacl_mask_to_mode(everyone.allowed);
+
+	/* Mask flags we can ignore */
+	x = S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD;
+
+	if (((richacl_mode_to_mask(mode >> 6) ^ owner.allowed)    & ~x) ||
+	    ((richacl_mode_to_mask(mode >> 3) ^ group.allowed)    & ~x) ||
+	    ((richacl_mode_to_mask(mode)      ^ everyone.allowed) & ~x))
+		return -1;
+
+	*mode_p = mode;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(richacl_equiv_mode);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index 3cd5e53..a865f37 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -190,5 +190,6 @@ extern unsigned int richacl_mode_to_mask(umode_t);
 extern int richacl_permission(struct inode *, const struct richacl *, int);
 extern void richacl_compute_max_masks(struct richacl *);
 extern int richacl_chmod(struct inode *, umode_t);
+extern int richacl_equiv_mode(const struct richacl *, umode_t *);
 
 #endif /* __RICHACL_H */
-- 
2.7.4

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Thread

[PATCH v25 00/22] Richacls (Core and Ext4) Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 14/22] richacl: Check if an acl is equivalent to a file mode Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 09/22] richacl: Compute maximum file masks from an acl Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 11/22] vfs: Add get_richacl and set_richacl inode operations Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 08/22] richacl: Permission check algorithm Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 01/22] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 10/22] vfs: Cache base_acl objects in inodes Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 02/22] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 03/22] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 04/22] vfs: Make the inode passed to inode_change_ok non-const Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 12/22] vfs: Cache richacl in struct inode Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 07/22] richacl: Permission mapping functions Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 13/22] richacl: Update the file masks in chmod() Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:10 +0200
  [PATCH v25 19/22] vfs: Add richacl permission checking Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 20/22] vfs: Move check_posix_acl and check_richacl out of fs/namei.c Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 15/22] richacl: Create-time inheritance Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 22/22] ext4: Add richacl feature flag Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 06/22] richacl: In-memory representation and helper functions Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 17/22] richacl: xattr mapping functions Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 21/22] ext4: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 16/22] richacl: Automatic Inheritance Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 18/22] richacl: Add richacl xattr handler Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200
  [PATCH v25 05/22] vfs: Add permission flags for setting file attributes Andreas Gruenbacher <agruenba@redhat.com> - 2016-08-16 13:20 +0200

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