@@ -318,15 +318,14 @@ static ssize_t dump_attr_read(struct file *filep, struct kobject *kobj,
return count;
}
-static struct dump_obj *create_dump_obj(uint32_t id, size_t size,
- uint32_t type)
+static void create_dump_obj(uint32_t id, size_t size, uint32_t type)
{
struct dump_obj *dump;
int rc;
dump = kzalloc(sizeof(*dump), GFP_KERNEL);
if (!dump)
- return NULL;
+ return;
dump->kobj.kset = dump_kset;
@@ -346,21 +345,39 @@ static struct dump_obj *create_dump_obj(uint32_t id, size_t size,
rc = kobject_add(&dump->kobj, NULL, "0x%x-0x%x", type, id);
if (rc) {
kobject_put(&dump->kobj);
- return NULL;
+ return;
}
+ /*
+ * As soon as the sysfs file for this dump is created/activated there is
+ * a chance the opal_errd daemon (or any userspace) might read and
+ * acknowledge the dump before kobject_uevent() is called. If that
+ * happens then there is a potential race between
+ * dump_ack_store->kobject_put() and kobject_uevent() which leads to a
+ * use-after-free of a kernfs object resulting in a kernel crash.
+ *
+ * To avoid that, we need to take a reference on behalf of the bin file,
+ * so that our reference remains valid while we call kobject_uevent().
+ * We then drop our reference before exiting the function, leaving the
+ * bin file to drop the last reference (if it hasn't already).
+ */
+
+ /* Take a reference for the bin file */
+ kobject_get(&dump->kobj);
rc = sysfs_create_bin_file(&dump->kobj, &dump->dump_attr);
- if (rc) {
+ if (rc == 0) {
+ kobject_uevent(&dump->kobj, KOBJ_ADD);
+
+ pr_info("%s: New platform dump. ID = 0x%x Size %u\n",
+ __func__, dump->id, dump->size);
+ } else {
+ /* Drop reference count taken for bin file */
kobject_put(&dump->kobj);
- return NULL;
}
- pr_info("%s: New platform dump. ID = 0x%x Size %u\n",
- __func__, dump->id, dump->size);
-
- kobject_uevent(&dump->kobj, KOBJ_ADD);
-
- return dump;
+ /* Drop our reference */
+ kobject_put(&dump->kobj);
+ return;
}
static irqreturn_t process_dump(int irq, void *data)