UBUNTU: SAUCE: (namespace) fuse: Translate ids in posix acl xattrs

BugLink: http://bugs.launchpad.net/bugs/1634964

Fuse currently lacks comprehensive support for posix ACLs, but
some fuse filesystems process the acl xattrs internally. For this
to continue to work the ids within the xattrs need to be mapped
into s_user_ns when written to the filesystem and mapped from
s_user_ns when read.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

fs/fuse/dir.c

@@ -13,6 +13,8 @@
 #include <linux/sched.h>
 #include <linux/namei.h>
 #include <linux/slab.h>
+#include <uapi/linux/xattr.h>
+#include <linux/posix_acl_xattr.h>
 
 static bool fuse_use_readdirplus(struct inode *dir, struct dir_context *ctx)
 {
@@ -1757,12 +1759,24 @@ static int fuse_setxattr(struct dentry *entry, const char *name,
 	struct inode *inode = d_inode(entry);
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	FUSE_ARGS(args);
+	void *buf = NULL;
 	struct fuse_setxattr_in inarg;
 	int err;
 
 	if (fc->no_setxattr)
 		return -EOPNOTSUPP;
 
+	if (!strcmp(name, XATTR_NAME_POSIX_ACL_ACCESS) ||
+	    !strcmp(name, XATTR_NAME_POSIX_ACL_DEFAULT)) {
+		buf = kmemdup(value, size, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+		err = posix_acl_fix_xattr_userns(inode->i_sb->s_user_ns,
+						 &init_user_ns, buf, size);
+		if (err)
+			goto out;
+	}
+
 	memset(&inarg, 0, sizeof(inarg));
 	inarg.size = size;
 	inarg.flags = flags;
@@ -1774,7 +1788,7 @@ static int fuse_setxattr(struct dentry *entry, const char *name,
 	args.in.args[1].size = strlen(name) + 1;
 	args.in.args[1].value = name;
 	args.in.args[2].size = size;
-	args.in.args[2].value = value;
+	args.in.args[2].value = buf ? buf : value;
 	err = fuse_simple_request(fc, &args);
 	if (err == -ENOSYS) {
 		fc->no_setxattr = 1;
@@ -1784,6 +1798,8 @@ static int fuse_setxattr(struct dentry *entry, const char *name,
 		fuse_invalidate_attr(inode);
 		fuse_update_ctime(inode);
 	}
+out:
+	kfree(buf);
 	return err;
 }
 
@@ -1820,8 +1836,16 @@ static ssize_t fuse_getxattr(struct dentry *entry, const char *name,
 		args.out.args[0].value = &outarg;
 	}
 	ret = fuse_simple_request(fc, &args);
-	if (!ret && !size)
-		ret = outarg.size;
+	if (!ret) {
+		if (!size) {
+			ret = outarg.size;
+		} else if (!strcmp(name, XATTR_NAME_POSIX_ACL_ACCESS) ||
+			   !strcmp(name, XATTR_NAME_POSIX_ACL_DEFAULT)) {
+			ret = posix_acl_fix_xattr_userns(&init_user_ns,
+							 inode->i_sb->s_user_ns,
+							 value, size);
+		}
+	}
 	if (ret == -ENOSYS) {
 		fc->no_getxattr = 1;
 		ret = -EOPNOTSUPP;