[PATCH 4.9 18/32] firmware: qemu_fw_cfg: fix kobject leak in probe error path

[Greg Kroah-Hartman]

From: Johan Hovold <johan@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx      # 4.6
Cc: Gabriel Somlo <somlo@xxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211201132528.30025-3-johan@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/firmware/qemu_fw_cfg.c |   13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

--- a/drivers/firmware/qemu_fw_cfg.c
+++ b/drivers/firmware/qemu_fw_cfg.c
@@ -461,15 +461,13 @@ static int fw_cfg_register_file(const st
 	/* 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->f.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->f.name);
@@ -478,9 +476,10 @@ static int fw_cfg_register_file(const st
 	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;
 }