Re: [RFC PATCH] Fix: membarrier: racy access to p->mm in membarrier_global_expedited()

[Jann Horn]

On Mon, Jan 28, 2019 at 7:27 PM Mathieu Desnoyers
<mathieu.desnoyers@xxxxxxxxxxxx> wrote:
> Jann Horn identified a racy access to p->mm in the global expedited
> command of the membarrier system call.
>
> The suggested fix is to hold the task_lock() around the accesses to
> p->mm and to the mm_struct membarrier_state field to guarantee the
> existence of the mm_struct.
>
> Link: https://lore.kernel.org/lkml/CAG48ez2G8ctF8dHS42TF37pThfr3y0RNOOYTmxvACm4u8Yu3cw@xxxxxxxxxxxxxx
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>

The patch looks good to me, and to be sure, I've also given it a spin
- I can't trigger a splat anymore. You can add:

Tested-by: Jann Horn <jannh@xxxxxxxxxx>