Re: [PATCH 1/1] kthread: introduce kthread_get_run() to fix __nbd_ioctl()

From: Oleg Nesterov
Date: Wed Oct 28 2015 - 10:31:00 EST


sorry for delay, I didn't have email access two days,

On 10/26, Markus Pargmann wrote:
> On Sun, Oct 25, 2015 at 03:27:13PM +0100, Oleg Nesterov wrote:
> > It is not safe to use the task_struct returned by kthread_run(threadfn)
> > if threadfn() can exit before the "owner" does kthread_stop(), nothing
> > protects this task_struct.
> >
> > So __nbd_ioctl() looks buggy; a killed nbd_thread_send() can exit, free
> > its task_struct, and then kthread_stop() can use the freed/reused memory.
> >
> > Add the new trivial helper, kthread_get_run(). Hopefully it will have more
> > users, this patch changes __nbd_ioctl() as an example.
> Thanks.
> Acked-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx>
> However I am not sure this is important for 4.3 final. This bug is
> present since at least 2008 (didn't look further).

Ah yes, I din't bother to check the history of this code, thanks.

So this bug is very old, no need to push the fix into 4.3.


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