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Groups > linux.kernel > #1282423

[PATCH v16 15/22] richacl: Check if an acl is equivalent to a file mode

From Andreas Gruenbacher <agruenba@redhat.com>
Newsgroups linux.kernel
Subject [PATCH v16 15/22] richacl: Check if an acl is equivalent to a file mode
Date 2015-12-02 22:20 +0100
Message-ID <qBmYG-4b2-11@gated-at.bofh.it> (permalink)
References <qBmP0-47N-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>
---
 fs/richacl_base.c       | 104 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/richacl.h |   1 +
 2 files changed, 105 insertions(+)

diff --git a/fs/richacl_base.c b/fs/richacl_base.c
index e4dd779..74e5cb5 100644
--- a/fs/richacl_base.c
+++ b/fs/richacl_base.c
@@ -382,3 +382,107 @@ __richacl_chmod(struct richacl *acl, umode_t mode)
 	return clone;
 }
 EXPORT_SYMBOL_GPL(__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 a2d5600..b7128bf 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -185,6 +185,7 @@ 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);
+extern int richacl_equiv_mode(const struct richacl *, umode_t *);
 
 /* richacl_inode.c */
 extern int richacl_permission(struct inode *, const struct richacl *, int);
-- 
2.5.0

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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

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