Re: [PATCH] ARM: mm: only adjust sections of valid mm structures

[Linus Walleij]

On Thu, Jun 27, 2019 at 11:33 PM Doug Berger <opendmb@xxxxxxxxx> wrote:

> A timing hazard exists when an early fork/exec thread begins
> exiting and sets its mm pointer to NULL while a separate core
> tries to update the section information.
>
> This commit ensures that the mm pointer is not NULL before
> setting its section parameters. The arguments provided by
> commit 11ce4b33aedc ("ARM: 8672/1: mm: remove tasklist locking
> from update_sections_early()") are equally valid for not
> requiring grabbing the task_lock around this check.
>
> Fixes: 08925c2f124f ("ARM: 8464/1: Update all mm structures with section adjustments")
> Signed-off-by: Doug Berger <opendmb@xxxxxxxxx>

Cc: stable@xxxxxxxxxxxxxxx ?

I'm not smart enough to say whether it is the right solution, but
I also want to test this on some boards I have. I suspect this
may be part of the problem I have with mounting root on a USB
stick on some early mpcore machines, so I might come back with
a Tested-by.

Yours,
Linus Walleij