powerpc/powernv: Restrict OPAL symbol map to only be readable by root

BugLink: https://bugs.launchpad.net/bugs/1848780

commit e7de4f7b upstream.

Currently the OPAL symbol map is globally readable, which seems bad as
it contains physical addresses.

Restrict it to root.

Fixes: c8742f85 ("powerpc/powernv: Expose OPAL firmware symbol map")
Cc: stable@vger.kernel.org # v3.19+
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190503075253.22798-1-ajd@linux.ibm.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

arch/powerpc/platforms/powernv/opal.c

@@ -580,7 +580,10 @@ static ssize_t symbol_map_read(struct file *fp, struct kobject *kobj,
 				       bin_attr->size);
 }
 
-static BIN_ATTR_RO(symbol_map, 0);
+static struct bin_attribute symbol_map_attr = {
+	.attr = {.name = "symbol_map", .mode = 0400},
+	.read = symbol_map_read
+};
 
 static void opal_export_symmap(void)
 {
@@ -597,10 +600,10 @@ static void opal_export_symmap(void)
 		return;
 
 	/* Setup attributes */
-	bin_attr_symbol_map.private = __va(be64_to_cpu(syms[0]));
-	bin_attr_symbol_map.size = be64_to_cpu(syms[1]);
+	symbol_map_attr.private = __va(be64_to_cpu(syms[0]));
+	symbol_map_attr.size = be64_to_cpu(syms[1]);
 
-	rc = sysfs_create_bin_file(opal_kobj, &bin_attr_symbol_map);
+	rc = sysfs_create_bin_file(opal_kobj, &symbol_map_attr);
 	if (rc)
 		pr_warn("Error %d creating OPAL symbols file\n", rc);
 }