On Fri 07-07-23 11:56:49, Luis Chamberlain wrote: > On Mon, Jul 03, 2023 at 03:47:22PM +0200, Michal Hocko wrote: > > On Fri 30-06-23 16:05:33, Luis Chamberlain wrote: > > [...] > > > What prevents code from racing the free with a random module_put() > > > called by some other piece of code? > > > > Wouldn't be ref count a garbage already? How can you race when freeing > > if module_put fail? > > It could yes, ie, so this risks at all being junk. Could you be more specific please? I still do not see a scenario where module string name would be junk while refcount itself would be a valid memory. > So best IMHO is > to tidy up all the get / puts and add respective tests to fix all > this mess with proper messages as needed. My cursory review of the > refcnt stuf is I see some races possible. It would likely be better to use refcount_t instead of atomic_t. > While I'd be happy to help debugging aids, adding accesses to random > memory for a string seems more risk prone. If there is really a scenario when module could be unloaded leaving dangling struct module behind then we have a real problem as this is exported to userspace IIRC. Not to mention module_get/put calls modifying memory (UAF). -- Michal Hocko SUSE Labs
