Re: [PATCH] binder: Don't use mmput() from shrinker function.

2020-07-16 Thread Michal Hocko
On Thu 16-07-20 22:41:14, Tetsuo Handa wrote: > On 2020/07/16 17:35, Michal Hocko wrote: [...] > > But in order for this to happen the shrinker would have to do the last > > put on the mm. But mm cannot go away from under uprobe_mmap so those two > > paths cannot race with each other. > > and mm1

Re: [PATCH] binder: Don't use mmput() from shrinker function.

2020-07-16 Thread Tetsuo Handa
On 2020/07/16 17:35, Michal Hocko wrote: > On Thu 16-07-20 08:36:52, Tetsuo Handa wrote: >> syzbot is reporting that mmput() from shrinker function has a risk of >> deadlock [1]. Don't start synchronous teardown of mm when called from >> shrinker function. > > Please add the actual lock dependency

Re: [PATCH] binder: Don't use mmput() from shrinker function.

2020-07-16 Thread Michal Hocko
On Thu 16-07-20 08:36:52, Tetsuo Handa wrote: > syzbot is reporting that mmput() from shrinker function has a risk of > deadlock [1]. Don't start synchronous teardown of mm when called from > shrinker function. Please add the actual lock dependency to the changelog. Anyway is this deadlock real?