firmware: qemu_fw_cfg: fix kobject leak in probe error path

commit 47a1db8e797da01a1309bf42e0c0d771d4e4d4f3 upstream.

An initialised kobject must be freed using kobject_put() to avoid
leaking associated resources (e.g. the object name).

Commit fe3c60684377 ("firmware: Fix a reference count leak.") "fixed"
the leak in the first error path of the file registration helper but
left the second one unchanged. This "fix" would however result in a NULL
pointer dereference due to the release function also removing the never
added entry from the fw_cfg_entry_cache list. This has now been
addressed.

Fix the remaining kobject leak by restoring the common error path and
adding the missing kobject_put().

Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device")
Cc: stable@vger.kernel.org      # 4.6
Cc: Gabriel Somlo <somlo@cmu.edu>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20211201132528.30025-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index 23ba850..f08e056 100644 (file)
--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -603,15 +603,13 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
        /* register entry under "/sys/firmware/qemu_fw_cfg/by_key/" */
        err = kobject_init_and_add(&entry->kobj, &fw_cfg_sysfs_entry_ktype,
                                   fw_cfg_sel_ko, "%d", entry->select);
-       if (err) {
-               kobject_put(&entry->kobj);
-               return err;
-       }
+       if (err)
+               goto err_put_entry;
 
        /* add raw binary content access */
        err = sysfs_create_bin_file(&entry->kobj, &fw_cfg_sysfs_attr_raw);
        if (err)
-               goto err_add_raw;
+               goto err_del_entry;
 
        /* try adding "/sys/firmware/qemu_fw_cfg/by_name/" symlink */
        fw_cfg_build_symlink(fw_cfg_fname_kset, &entry->kobj, entry->name);
@@ -620,9 +618,10 @@ static int fw_cfg_register_file(const struct fw_cfg_file *f)
        fw_cfg_sysfs_cache_enlist(entry);
        return 0;
 
-err_add_raw:
+err_del_entry:
        kobject_del(&entry->kobj);
-       kfree(entry);
+err_put_entry:
+       kobject_put(&entry->kobj);
        return err;
 }