Re: [PATCH 4/4] mm/gup: Assert that the mmap lock is held in __get_user_pages()

Jason Gunthorpe
2020-09-30T12:32:24Z

On Tue, Sep 29, 2020 at 06:20:01PM -0700, Jann Horn wrote:
> After having cleaned up all GUP callers (except for the atomisp staging
> driver, which currently gets mmap locking completely wrong [1]) to always
> ensure that they hold the mmap lock when calling into GUP (unless the mm is
> not yet globally visible), add an assertion to make sure it stays that way
> going forward.
>
> [1] https://lore.kernel.org/lkml/CAG48ez3tZAb9JVhw4T5e-i=h2_DUZxfNRTDsagSRCVazNXx5qA@mail.gmail.com/
>
> Signed-off-by: Jann Horn <jannh@google.com>
> ---
> mm/gup.c | 2 ++
> 1 file changed, 2 insertions(+)

I'm happy to see this, I have observed many cases of missing locking
here.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Thanks,
Jason