Commit fe3c60684377 ("firmware: Fix a reference count leak.") "fixed" a kobject leak in the file registration helper by properly calling kobject_put() for the entry in case registration of the object fails (e.g. due to a name collision).

This would however result in a NULL pointer dereference when the release function tries to remove the never added entry from the fw_cfg_entry_cache list.

Fix this by moving the list-removal out of the release function.

Note that the offending commit was one of the benign looking umn.edu fixes which was reviewed but not reverted. [1][2]

[1] https://lore.kernel.org/r/202105051005.49BFABCE@keescook [2] https://lore.kernel.org/all/YIg7ZOZvS3a8LjSv@kroah.com

Fixes: fe3c60684377 ("firmware: Fix a reference count leak.") Cc: stable@vger.kernel.org # 5.8 Cc: Qiushi Wu wu000273@umn.edu Cc: Kees Cook keescook@chromium.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Johan Hovold johan@kernel.org --- drivers/firmware/qemu_fw_cfg.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/firmware/qemu_fw_cfg.c b/drivers/firmware/qemu_fw_cfg.c index 172c751a4f6c..a9c64ebfc49a 100644 --- a/drivers/firmware/qemu_fw_cfg.c +++ b/drivers/firmware/qemu_fw_cfg.c @@ -388,9 +388,7 @@ static void fw_cfg_sysfs_cache_cleanup(void) struct fw_cfg_sysfs_entry *entry, *next;

list_for_each_entry_safe(entry, next, &fw_cfg_entry_cache, list) { - /* will end up invoking fw_cfg_sysfs_cache_delist() - * via each object's release() method (i.e. destructor) - */ + fw_cfg_sysfs_cache_delist(entry); kobject_put(&entry->kobj); } } @@ -448,7 +446,6 @@ static void fw_cfg_sysfs_release_entry(struct kobject *kobj) { struct fw_cfg_sysfs_entry *entry = to_entry(kobj);

- fw_cfg_sysfs_cache_delist(entry); kfree(entry); }