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[PATCH v9 07/43] richacl: Permission mapping functions

From Andreas Gruenbacher <agruenba@redhat.com>
Newsgroups linux.kernel
Subject [PATCH v9 07/43] richacl: Permission mapping functions
Date 2015-10-05 22:20 +0200
Message-ID <qgkoO-Wa-3@gated-at.bofh.it> (permalink)
References <qgjM5-8oR-9@gated-at.bofh.it>
Organization linux.* mail to news gateway

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We need to map from POSIX permissions to NFSv4 permissions when a
chmod() is done, from NFSv4 permissions to POSIX permissions when an acl
is set (which implicitly sets the file permission bits), and from the
MAY_READ/MAY_WRITE/MAY_EXEC/MAY_APPEND flags to NFSv4 permissions when
doing an access check in a richacl.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/richacl_base.c       | 117 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/richacl.h |  47 ++++++++++++++++++-
 2 files changed, 163 insertions(+), 1 deletion(-)

diff --git a/fs/richacl_base.c b/fs/richacl_base.c
index 6d9a073..063dbe4 100644
--- a/fs/richacl_base.c
+++ b/fs/richacl_base.c
@@ -65,3 +65,120 @@ richace_copy(struct richace *to, const struct richace *from)
 {
 	memcpy(to, from, sizeof(struct richace));
 }
+
+/*
+ * richacl_mask_to_mode  -  compute the file permission bits from mask
+ * @mask:	%RICHACE_* permission mask
+ *
+ * Compute the file permission bits corresponding to a particular set of
+ * richacl permissions.
+ *
+ * See richacl_masks_to_mode().
+ */
+static int
+richacl_mask_to_mode(unsigned int mask)
+{
+	int mode = 0;
+
+	if (mask & RICHACE_POSIX_MODE_READ)
+		mode |= S_IROTH;
+	if (mask & RICHACE_POSIX_MODE_WRITE)
+		mode |= S_IWOTH;
+	if (mask & RICHACE_POSIX_MODE_EXEC)
+		mode |= S_IXOTH;
+
+	return mode;
+}
+
+/**
+ * richacl_masks_to_mode  -  compute file permission bits from file masks
+ *
+ * When setting a richacl, we set the file permission bits to indicate maximum
+ * permissions: for example, we set the Write permission when a mask contains
+ * RICHACE_APPEND_DATA even if it does not also contain RICHACE_WRITE_DATA.
+ *
+ * Permissions which are not in RICHACE_POSIX_MODE_READ,
+ * RICHACE_POSIX_MODE_WRITE, or RICHACE_POSIX_MODE_EXEC cannot be represented
+ * in the file permission bits.  Such permissions can still be effective, but
+ * not for new files or after a chmod(); they must be explicitly enabled in the
+ * richacl.
+ */
+int
+richacl_masks_to_mode(const struct richacl *acl)
+{
+	return richacl_mask_to_mode(acl->a_owner_mask) << 6 |
+	       richacl_mask_to_mode(acl->a_group_mask) << 3 |
+	       richacl_mask_to_mode(acl->a_other_mask);
+}
+EXPORT_SYMBOL_GPL(richacl_masks_to_mode);
+
+/**
+ * richacl_mode_to_mask  - compute a file mask from the lowest three mode bits
+ *
+ * When the file permission bits of a file are set with chmod(), this specifies
+ * the maximum permissions that processes will get.  All permissions beyond
+ * that will be removed from the file masks, and become ineffective.
+ */
+unsigned int
+richacl_mode_to_mask(mode_t mode)
+{
+	unsigned int mask = 0;
+
+	if (mode & S_IROTH)
+		mask |= RICHACE_POSIX_MODE_READ;
+	if (mode & S_IWOTH)
+		mask |= RICHACE_POSIX_MODE_WRITE;
+	if (mode & S_IXOTH)
+		mask |= RICHACE_POSIX_MODE_EXEC;
+
+	return mask;
+}
+
+/**
+ * richacl_want_to_mask  - convert the iop->permission want argument to a mask
+ * @want:	@want argument of the permission inode operation
+ *
+ * When checking for append, @want is (MAY_WRITE | MAY_APPEND).
+ *
+ * Richacls use the iop->may_create and iop->may_delete hooks which are used
+ * for checking if creating and deleting files is allowed.  These hooks do not
+ * use richacl_want_to_mask(), so we do not have to deal with mapping MAY_WRITE
+ * to RICHACE_ADD_FILE, RICHACE_ADD_SUBDIRECTORY, and RICHACE_DELETE_CHILD
+ * here.
+ */
+unsigned int
+richacl_want_to_mask(unsigned int want)
+{
+	unsigned int mask = 0;
+
+	if (want & MAY_READ)
+		mask |= RICHACE_READ_DATA;
+	if (want & MAY_DELETE_SELF)
+		mask |= RICHACE_DELETE;
+	if (want & MAY_TAKE_OWNERSHIP)
+		mask |= RICHACE_WRITE_OWNER;
+	if (want & MAY_CHMOD)
+		mask |= RICHACE_WRITE_ACL;
+	if (want & MAY_SET_TIMES)
+		mask |= RICHACE_WRITE_ATTRIBUTES;
+	if (want & MAY_EXEC)
+		mask |= RICHACE_EXECUTE;
+	/*
+	 * differentiate MAY_WRITE from these request
+	 */
+	if (want & (MAY_APPEND |
+		    MAY_CREATE_FILE | MAY_CREATE_DIR |
+		    MAY_DELETE_CHILD)) {
+		if (want & MAY_APPEND)
+			mask |= RICHACE_APPEND_DATA;
+		if (want & MAY_CREATE_FILE)
+			mask |= RICHACE_ADD_FILE;
+		if (want & MAY_CREATE_DIR)
+			mask |= RICHACE_ADD_SUBDIRECTORY;
+		if (want & MAY_DELETE_CHILD)
+			mask |= RICHACE_DELETE_CHILD;
+	} else if (want & MAY_WRITE)
+		mask |= RICHACE_WRITE_DATA;
+	return mask;
+}
+EXPORT_SYMBOL_GPL(richacl_want_to_mask);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index bfa94bb..9c8f298 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -126,6 +126,49 @@ struct richacl {
 	RICHACE_WRITE_OWNER |					\
 	RICHACE_SYNCHRONIZE)
 
+/*
+ * The POSIX permissions are supersets of the following NFSv4 permissions:
+ *
+ *  - MAY_READ maps to READ_DATA or LIST_DIRECTORY, depending on the type
+ *    of the file system object.
+ *
+ *  - MAY_WRITE maps to WRITE_DATA or RICHACE_APPEND_DATA for files, and to
+ *    ADD_FILE, RICHACE_ADD_SUBDIRECTORY, or RICHACE_DELETE_CHILD for directories.
+ *
+ *  - MAY_EXECUTE maps to RICHACE_EXECUTE.
+ *
+ *  (Some of these NFSv4 permissions have the same bit values.)
+ */
+#define RICHACE_POSIX_MODE_READ (			\
+		RICHACE_READ_DATA |		\
+		RICHACE_LIST_DIRECTORY)
+#define RICHACE_POSIX_MODE_WRITE (			\
+		RICHACE_WRITE_DATA |		\
+		RICHACE_ADD_FILE |			\
+		RICHACE_APPEND_DATA |		\
+		RICHACE_ADD_SUBDIRECTORY |		\
+		RICHACE_DELETE_CHILD)
+#define RICHACE_POSIX_MODE_EXEC RICHACE_EXECUTE
+#define RICHACE_POSIX_MODE_ALL (			\
+		RICHACE_POSIX_MODE_READ |		\
+		RICHACE_POSIX_MODE_WRITE |		\
+		RICHACE_POSIX_MODE_EXEC)
+/*
+ * These permissions are always allowed
+ * no matter what the acl says.
+ */
+#define RICHACE_POSIX_ALWAYS_ALLOWED (	\
+		RICHACE_SYNCHRONIZE |	\
+		RICHACE_READ_ATTRIBUTES |	\
+		RICHACE_READ_ACL)
+/*
+ * The owner is implicitly granted
+ * these permissions under POSIX.
+ */
+#define RICHACE_POSIX_OWNER_ALLOWED (		\
+		RICHACE_WRITE_ATTRIBUTES |		\
+		RICHACE_WRITE_OWNER |		\
+		RICHACE_WRITE_ACL)
 /**
  * richacl_get  -  grab another reference to a richacl handle
  */
@@ -251,6 +294,8 @@ richace_is_same_identifier(const struct richace *a, const struct richace *b)
 extern struct richacl *richacl_alloc(int, gfp_t);
 extern struct richacl *richacl_clone(const struct richacl *, gfp_t);
 extern void richace_copy(struct richace *, const struct richace *);
-
+extern int richacl_masks_to_mode(const struct richacl *);
+extern unsigned int richacl_mode_to_mask(mode_t);
+extern unsigned int richacl_want_to_mask(unsigned int);
 
 #endif /* __RICHACL_H */
-- 
2.5.0

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Thread

[PATCH v9 00/43] Richacls Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:40 +0200
  [PATCH v9 22/43] richacl: acl editing helper functions Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:40 +0200
  [PATCH v9 12/43] vfs: Cache richacl in struct inode Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:40 +0200
  [PATCH v9 38/43] sunrpc: Add xdr_init_encode_pages Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 42/43] nfs: Add support for the v4.1 dacl attribute Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 34/43] nfsd: Add support for the MAY_CREATE_{FILE,DIR} permissions Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 35/43] richacl: Add support for unmapped identifiers Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 28/43] richacl: Apply the file masks to a richacl Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 39/43] nfs: Fix GETATTR bitmap verification Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 37/43] sunrpc: Allow to demand-allocate pages to encode into Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 36/43] ext4: Don't allow unmapped identifiers in richacls Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 40/43] nfs: Remove unused xdr page offsets in getacl/setacl arguments Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 41/43] nfs: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 31/43] nfsd: Use richacls as internal acl representation Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 30/43] nfsd: Keep list of acls to dispose of in compoundargs Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 43/43] richacl: uapi header split Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 33/43] nfsd: Add support for the v4.1 dacl attribute Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 21:50 +0200
  [PATCH v9 32/43] nfsd: Add richacl support Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 22:00 +0200
  [PATCH v9 29/43] richacl: Create richacl from mode values Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 22:00 +0200
  [PATCH v9 11/43] vfs: Add get_richacl and set_richacl inode operations Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 22:10 +0200
  [PATCH v9 21/43] ext4: Add richacl feature flag Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 22:10 +0200
  [PATCH v9 07/43] richacl: Permission mapping functions Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 22:20 +0200
  [PATCH v9 02/43] vfs: Add MAY_CREATE_FILE and MAY_CREATE_DIR permission flags Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-05 22:20 +0200
  Re: [PATCH v9 00/43] Richacls Pavel Machek <pavel@ucw.cz> - 2015-10-06 11:10 +0200
    Re: [PATCH v9 00/43] Richacls Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-06 14:50 +0200
      Re: [PATCH v9 00/43] Richacls James Morris <jmorris@namei.org> - 2015-10-07 09:40 +0200
        Re: [PATCH v9 00/43] Richacls Austin S Hemmelgarn <ahferroin7@gmail.com> - 2015-10-07 15:30 +0200
        Re: [PATCH v9 00/43] Richacls Andreas Gruenbacher <agruenba@redhat.com> - 2015-10-07 15:50 +0200

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