Add Hooks for Linux Xattr Operations

The Linux specific xattr operations have all been located in the
file zpl_xattr.c.  These functions primarily rely on the reworked
zfs_* functions to do their job.  They are also responsible for
converting the possible Solaris style error codes to negative
Linux errors.

1 files changed, 432 insertions, 0 deletions

diff --git a/module/zfs/zpl_xattr.c b/module/zfs/zpl_xattr.c
new file mode 100644
index 000000000..910500a72
--- /dev/null
+++ b/module/zfs/zpl_xattr.c
@@ -0,0 +1,432 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2011, Lawrence Livermore National Security, LLC.
+ *
+ * Extended attributes (xattr) on Solaris are implemented as files
+ * which exist in a hidden xattr directory.  These extended attributes
+ * can be accessed using the attropen() system call which opens
+ * the extended attribute.  It can then be manipulated just like
+ * a standard file descriptor.  This has a couple advantages such
+ * as practically no size limit on the file, and the extended
+ * attributes permissions may differ from those of the parent file.
+ * This interface is really quite clever, but it's also completely
+ * different than what is supported on Linux.
+ *
+ * Under Linux extended attributes are manipulated by the system
+ * calls getxattr(2), setxattr(2), and listxattr(2).  They consider
+ * extended attributes to be name/value pairs where the name is a
+ * NULL terminated string.  The name must also include one of the
+ * following name space prefixes:
+ *
+ *   user     - No restrictions and is available to user applications.
+ *   trusted  - Restricted to kernel and root (CAP_SYS_ADMIN) use.
+ *   system   - Used for access control lists (system.nfs4_acl, etc).
+ *   security - Used by SELinux to store a files security context.
+ *
+ * This Linux interface is implemented internally using the more
+ * flexible Solaris style extended attributes.  Every extended
+ * attribute is store as a file in a hidden directory associated
+ * with the parent file.  This ensures on disk compatibility with
+ * zfs implementations on other platforms (Solaris, FreeBSD, MacOS).
+ *
+ * One consequence of this implementation is that when an extended
+ * attribute is manipulated an inode is created.  This inode will
+ * exist in the Linux inode cache but there will be no associated
+ * entry in the dentry cache which references it.  This is safe
+ * but it may result in some confusion.
+ *
+ * Longer term I would like to see the 'security.selinux' extended
+ * attribute moved to a SA.  This should significantly improve
+ * performance on a SELinux enabled system by minimizing the
+ * number of seeks required to access a file.  However, for now
+ * this xattr is still stored in a file because I'm pretty sure
+ * adding a new SA will break on-disk compatibility.
+ */
+
+
+#include <sys/zfs_vfsops.h>
+#include <sys/zfs_vnops.h>
+#include <sys/zfs_znode.h>
+#include <sys/vfs.h>
+#include <sys/zpl.h>
+
+typedef struct xattr_filldir {
+	size_t size;
+	size_t offset;
+	char *buf;
+	struct inode *inode;
+} xattr_filldir_t;
+
+static int
+zpl_xattr_filldir(void *arg, const char *name, int name_len,
+    loff_t offset, uint64_t objnum, unsigned int d_type)
+{
+	xattr_filldir_t *xf = arg;
+
+	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
+		if (!(ITOZSB(xf->inode)->z_flags & ZSB_XATTR_USER))
+			return (0);
+
+	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
+		if (!capable(CAP_SYS_ADMIN))
+			return (0);
+
+	/* When xf->buf is NULL only calculate the required size. */
+	if (xf->buf) {
+		if (xf->offset + name_len + 1 > xf->size)
+			return (-ERANGE);
+
+		memcpy(xf->buf + xf->offset, name, name_len);
+		xf->buf[xf->offset + name_len] = '\0';
+	}
+
+	xf->offset += (name_len + 1);
+
+	return (0);
+}
+
+ssize_t
+zpl_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
+{
+	struct inode *ip = dentry->d_inode;
+	struct inode *dxip = NULL;
+	loff_t pos = 3;  /* skip '.', '..', and '.zfs' entries. */
+	cred_t *cr;
+	int error;
+	xattr_filldir_t xf = { buffer_size, 0, buffer, ip };
+
+	cr = (cred_t *)get_current_cred();
+
+	/* Lookup the xattr directory */
+	error = -zfs_lookup(ip, NULL, &dxip, LOOKUP_XATTR, cr, NULL, NULL);
+	if (error) {
+		if (error == -ENOENT)
+			error = 0;
+
+		goto out;
+	}
+
+	/* Fill provided buffer via zpl_zattr_filldir helper */
+	error = -zfs_readdir(dxip, (void *)&xf, zpl_xattr_filldir, &pos, cr);
+	if (error)
+		goto out;
+
+	error = xf.offset;
+out:
+	if (dxip)
+		iput(dxip);
+
+	put_cred(cr);
+
+	return (error);
+}
+
+static int
+zpl_xattr_get(struct inode *ip, const char *name, void *buf, size_t size)
+{
+	struct inode *dxip = NULL;
+	struct inode *xip = NULL;
+	cred_t *cr;
+	int error;
+
+	cr = (cred_t *)get_current_cred();
+
+	/* Lookup the xattr directory */
+	error = -zfs_lookup(ip, NULL, &dxip, LOOKUP_XATTR, cr, NULL, NULL);
+	if (error)
+		goto out;
+
+	/* Lookup a specific xattr name in the directory */
+	error = -zfs_lookup(dxip, (char *)name, &xip, 0, cr, NULL, NULL);
+	if (error)
+		goto out;
+
+	if (!size) {
+		error = i_size_read(xip);
+		goto out;
+	}
+
+	error = zpl_read_common(xip, buf, size, 0, UIO_SYSSPACE, 0, cr);
+out:
+	if (xip)
+		iput(xip);
+
+	if (dxip)
+		iput(dxip);
+
+	put_cred(cr);
+
+	if (error == -ENOENT)
+		error = -ENODATA;
+
+	return (error);
+}
+
+static int
+zpl_xattr_set(struct inode *ip, const char *name, const void *value,
+    size_t size, int flags)
+{
+	struct inode *dxip = NULL;
+	struct inode *xip = NULL;
+	vattr_t *vap = NULL;
+	cred_t *cr;
+	ssize_t wrote;
+	int error;
+
+	cr = (cred_t *)get_current_cred();
+
+	/* Lookup the xattr directory and create it if required. */
+	error = -zfs_lookup(ip, NULL, &dxip, LOOKUP_XATTR | CREATE_XATTR_DIR,
+	    cr, NULL, NULL);
+	if (error)
+		goto out;
+
+	/*
+	 * Lookup a specific xattr name in the directory, two failure modes:
+	 *   XATTR_CREATE: fail if xattr already exists
+	 *   XATTR_REMOVE: fail if xattr does not exist
+	 */
+	error = -zfs_lookup(dxip, (char *)name, &xip, 0, cr, NULL, NULL);
+	if (error) {
+		if (error != -ENOENT)
+			goto out;
+
+		if ((error == -ENOENT) && (flags & XATTR_REPLACE))
+			goto out;
+	} else {
+		error = -EEXIST;
+		if (flags & XATTR_CREATE)
+			goto out;
+	}
+	error = 0;
+
+	/* Remove a specific name xattr when value is set to NULL. */
+	if (value == NULL) {
+		if (xip)
+			error = -zfs_remove(dxip, (char *)name, cr);
+
+		goto out;
+	}
+
+	/* Lookup failed create a new xattr. */
+	if (xip == NULL) {
+		vap = kmem_zalloc(sizeof(vattr_t), KM_SLEEP);
+		vap->va_mode = S_IFREG | 0644;
+		vap->va_mask = ATTR_MODE;
+		vap->va_uid = current_fsuid();
+		vap->va_gid = current_fsgid();
+
+		error = -zfs_create(dxip, (char *)name, vap, 0, 0644, &xip,
+		    cr, 0, NULL);
+		if (error)
+			goto out;
+	}
+
+	ASSERT(xip != NULL);
+	wrote = zpl_write_common(xip, value, size, 0, UIO_SYSSPACE, 0, cr);
+	if (wrote < 0)
+		error = wrote;
+
+out:
+	if (vap)
+		kmem_free(vap, sizeof(vattr_t));
+
+	if (xip)
+		iput(xip);
+
+	if (dxip)
+		iput(dxip);
+
+	put_cred(cr);
+	if (error == -ENOENT)
+		error = -ENODATA;
+
+	ASSERT3S(error, <=, 0);
+
+	return (error);
+}
+
+static int
+zpl_xattr_user_get(struct inode *ip, const char *name,
+    void *buffer, size_t size)
+{
+	char *xattr_name;
+	int error;
+
+	if (strcmp(name, "") == 0)
+		return -EINVAL;
+
+	if (!(ITOZSB(ip)->z_flags & ZSB_XATTR_USER))
+		return -EOPNOTSUPP;
+
+	xattr_name = kmem_asprintf("%s%s", XATTR_USER_PREFIX, name);
+	error = zpl_xattr_get(ip, xattr_name, buffer, size);
+	strfree(xattr_name);
+
+	return (error);
+}
+
+static int
+zpl_xattr_user_set(struct inode *ip, const char *name,
+    const void *value, size_t size, int flags)
+{
+	char *xattr_name;
+	int error;
+
+	if (strcmp(name, "") == 0)
+		return -EINVAL;
+
+	if (!(ITOZSB(ip)->z_flags & ZSB_XATTR_USER))
+		return -EOPNOTSUPP;
+
+	xattr_name = kmem_asprintf("%s%s", XATTR_USER_PREFIX, name);
+	error = zpl_xattr_set(ip, xattr_name, value, size, flags);
+	strfree(xattr_name);
+
+	return (error);
+}
+
+struct xattr_handler zpl_xattr_user_handler = {
+	.prefix	= XATTR_USER_PREFIX,
+	.get	= zpl_xattr_user_get,
+	.set	= zpl_xattr_user_set,
+};
+
+static int
+zpl_xattr_trusted_get(struct inode *ip, const char *name,
+    void *buffer, size_t size)
+{
+	char *xattr_name;
+	int error;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	if (strcmp(name, "") == 0)
+		return -EINVAL;
+
+	xattr_name = kmem_asprintf("%s%s", XATTR_TRUSTED_PREFIX, name);
+	error = zpl_xattr_get(ip, xattr_name, buffer, size);
+	strfree(xattr_name);
+
+	return (error);
+}
+
+static int
+zpl_xattr_trusted_set(struct inode *ip, const char *name,
+    const void *value, size_t size, int flags)
+{
+	char *xattr_name;
+	int error;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	if (strcmp(name, "") == 0)
+		return -EINVAL;
+
+	xattr_name = kmem_asprintf("%s%s", XATTR_TRUSTED_PREFIX, name);
+	error = zpl_xattr_set(ip, xattr_name, value, size, flags);
+	strfree(xattr_name);
+
+	return (error);
+}
+
+struct xattr_handler zpl_xattr_trusted_handler = {
+	.prefix	= XATTR_TRUSTED_PREFIX,
+	.get	= zpl_xattr_trusted_get,
+	.set	= zpl_xattr_trusted_set,
+};
+
+static int
+zpl_xattr_security_get(struct inode *ip, const char *name,
+    void *buffer, size_t size)
+{
+	char *xattr_name;
+	int error;
+
+	if (strcmp(name, "") == 0)
+		return -EINVAL;
+
+	xattr_name = kmem_asprintf("%s%s", XATTR_SECURITY_PREFIX, name);
+	error = zpl_xattr_get(ip, xattr_name, buffer, size);
+	strfree(xattr_name);
+
+	return (error);
+}
+
+static int
+zpl_xattr_security_set(struct inode *ip, const char *name,
+    const void *value, size_t size, int flags)
+{
+	char *xattr_name;
+	int error;
+
+	if (strcmp(name, "") == 0)
+		return -EINVAL;
+
+	xattr_name = kmem_asprintf("%s%s", XATTR_SECURITY_PREFIX, name);
+	error = zpl_xattr_set(ip, xattr_name, value, size, flags);
+	strfree(xattr_name);
+
+	return (error);
+}
+
+int
+zpl_xattr_security_init(struct inode *ip, struct inode *dip)
+{
+        int error;
+        size_t len;
+        void *value;
+        char *name;
+
+        error = security_inode_init_security(ip, dip, &name, &value, &len);
+        if (error) {
+                if (error == -EOPNOTSUPP)
+                        return 0;
+
+                return (error);
+        }
+
+	error = zpl_xattr_security_set(ip, name, value, len, 0);
+
+        kfree(name);
+        kfree(value);
+
+        return (error);
+}
+
+struct xattr_handler zpl_xattr_security_handler = {
+	.prefix	= XATTR_SECURITY_PREFIX,
+	.get	= zpl_xattr_security_get,
+	.set	= zpl_xattr_security_set,
+};
+
+struct xattr_handler *zpl_xattr_handlers[] = {
+	&zpl_xattr_security_handler,
+	&zpl_xattr_trusted_handler,
+	&zpl_xattr_user_handler,
+#ifdef HAVE_POSIX_ACLS
+	&zpl_xattr_acl_access_handler,
+        &zpl_xattr_acl_default_handler,
+#endif /* HAVE_POSIX_ACLS */
+};