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

Greg Kroah-Hartman
2022-03-07T09:20:06Z

From: Johan Hovold <johan@kernel.org>

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>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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;
}