On Wed, Feb 19, 2020 at 07:32:13PM -0800, Cong Wang wrote: > On Tue, Feb 18, 2020 at 2:05 PM Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > > > > On Tue, Feb 18, 2020 at 01:40:26PM -0800, Cong Wang wrote: > > > On Tue, Feb 18, 2020 at 1:35 PM Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > > > > > > > > On Wed, Feb 12, 2020 at 10:53:52PM -0800, Cong Wang wrote: > > > > > Before releasing the global mutex, we only unlink the hashtable > > > > > from the hash list, its proc file is still not unregistered at > > > > > this point. So syzbot could trigger a race condition where a > > > > > parallel htable_create() could register the same file immediately > > > > > after the mutex is released. > > > > > > > > > > Move htable_remove_proc_entry() back to mutex protection to > > > > > fix this. And, fold htable_destroy() into htable_put() to make > > > > > the code slightly easier to understand. > > > > > > > > Probably revert previous one? > > > > > > The hung task could appear again if we move the cleanup > > > back under mutex. > > > > How could the hung task appear again by reverting > > c4a3922d2d20c710f827? Please elaborate. > > Because the cfg.max could be as large as 8*HASHLIMIT_MAX_SIZE: > > 311 if (hinfo->cfg.max == 0) > 312 hinfo->cfg.max = 8 * hinfo->cfg.size; > 313 else if (hinfo->cfg.max < hinfo->cfg.size) > 314 hinfo->cfg.max = hinfo->cfg.size; > > Not sure whether we can finish cleaning up 8*HASHLIMIT_MAX_SIZE > entries within the time a hung task tolerates. This largely depends on > how much contention the spinlock has, at least I don't want to bet > on it. Please, resend. Thanks.
