2016-09-28 11:08 GMT+08:00 Liping Zhang <zlpnobody@xxxxxxxxx>: > Hi Feng, > > 2016-09-28 9:23 GMT+08:00 Feng Gao <gfree.wind@xxxxxxxxx>: >> Hi Aaraon, >> >> On Tue, Sep 27, 2016 at 9:38 PM, Aaron Conole <aconole@xxxxxxxxxx> wrote: >>> It's possible for nf_hook_entry_head to return NULL if two >>> nf_unregister_net_hook calls happen simultaneously with a single hook >> >> The critical region of nf_unregister_net_hook is protected by &nf_hook_mutex. >> When it would be called simultaneously? > > This is unrelated to race condition. > > Suppose that only the last nf_hook_entry exist, and two callers want to do > un-register work. > > The first one will remove it successfully, after the end of the work, the > second one will enter the critical section, but it will see the NULL pointer. > Because the last nf_hook_entry was already removed by the first one. > >> >> Regards >> Feng >> >>> entry in the list. This fix ensures that no null pointer dereference >>> could occur when such a race happens. >>> >>> Signed-off-by: Aaron Conole <aconole@xxxxxxxxxx> I read the commit log again, I think the description here is a little confusing indeed. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
