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From: Andreas Gruenbacher <agruenba@redhat.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
	Christoph Hellwig <hch@infradead.org>,
	"Theodore Ts'o" <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Jeff Layton <jlayton@poochiereds.net>,
	Trond Myklebust <trond.myklebust@primarydata.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Dave Chinner <david@fromorbit.com>,
	linux-ext4@vger.kernel.org, xfs@oss.sgi.com,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	linux-api@vger.kernel.org
Subject: [PATCH v26 13/21] richacl: Check if an acl is equivalent to a file mode
Date: Thu, 29 Sep 2016 01:29:32 +0200	[thread overview]
Message-ID: <1475105380-22837-14-git-send-email-agruenba@redhat.com> (raw)
In-Reply-To: <1475105380-22837-1-git-send-email-agruenba@redhat.com>

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

  parent reply	other threads:[~2016-09-28 23:34 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-28 23:29 [PATCH v25 00/21] Richacls (Core and Ext4) Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 01/21] vfs: Add IS_ACL() and IS_RICHACL() tests Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 02/21] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 03/21] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD " Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 04/21] vfs: Add permission flags for setting file attributes Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 05/21] richacl: In-memory representation and helper functions Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 06/21] richacl: Permission mapping functions Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 07/21] richacl: Permission check algorithm Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 08/21] richacl: Compute maximum file masks from an acl Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 09/21] vfs: Cache base_acl objects in inodes Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 10/21] vfs: Add get_richacl and set_richacl inode operations Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 11/21] vfs: Cache richacl in struct inode Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 12/21] richacl: Update the file masks in chmod() Andreas Gruenbacher
2016-09-28 23:29 ` Andreas Gruenbacher [this message]
2016-09-28 23:29 ` [PATCH v26 14/21] richacl: Create-time inheritance Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 15/21] richacl: Automatic Inheritance Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 16/21] richacl: xattr mapping functions Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 17/21] richacl: Add richacl xattr handler Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 18/21] vfs: Add richacl permission checking Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 19/21] vfs: Move check_posix_acl and check_richacl out of fs/namei.c Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 20/21] ext4: Add richacl support Andreas Gruenbacher
2016-09-28 23:29 ` [PATCH v26 21/21] ext4: Add richacl feature flag Andreas Gruenbacher
2016-09-30 16:11 ` [PATCH v25 00/21] Richacls (Core and Ext4) J. Bruce Fields

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