[PATCH] fs, cifs: convert tcon_link.tl_count from atomic_t to refcount_t
aaptel at suse.com
Mon Oct 30 15:03:02 UTC 2017
Elena Reshetova <elena.reshetova at intel.com> writes:
> atomic_t variables are currently used to implement reference
> counters with the following properties:
> - counter is initialized to 1 using atomic_set()
> - a resource is freed upon counter reaching zero
> - once counter reaches zero, its further
> increments aren't allowed
> - counter schema uses basic atomic operations
> (set, inc, inc_not_zero, dec_and_test, etc.)
> Such atomic variables should be converted to a newly provided
> refcount_t type and API that prevents accidental counter overflows
> and underflows. This is important since overflows and underflows
> can lead to use-after-free situation and be exploitable.
> The variable tcon_link.tl_count is used as pure reference counter.
> Convert it to refcount_t and fix up the operations.
> - cifs_get_tlink(tlink);
> + refcount_set(&tlink->tl_count, 1);
Since cifs_get_tlink() basically only increments the reference count and
given that this is a new tlink I also think this replacement is ok.
Looks good to me and passes 'make C=1'.
Reviewed-by: Aurelien Aptel <aaptel at suse.com>
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3
SUSE Linux GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
More information about the samba-technical