linux-kernel - [PATCH 2/4] firmware: qemu_fw_cfg: fix kobject leak in probe error path

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Message-Id: <20211201132528.30025-3-johan@kernel.org>
Date:   Wed,  1 Dec 2021 14:25:26 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Gabriel Somlo <somlo@....edu>,
        "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>, qemu-devel@...gnu.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        stable@...r.kernel.org
Subject: [PATCH 2/4] firmware: qemu_fw_cfg: fix kobject leak in probe error path

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@...r.kernel.org      # 4.6
Cc: Gabriel Somlo <somlo@....edu>
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/firmware/qemu_fw_cfg.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c
index a9c64ebfc49a..ccb7ed62452f 100644
--- 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;
 }
 
-- 
2.32.0