linux-kernel - Re: [PATCH] optee: remove address tag in check_mem

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Date:   Mon, 12 Oct 2020 13:35:06 +0200
From:   Jens Wiklander <jens.wiklander@...aro.org>
To:     Volodymyr Babchuk <Volodymyr_Babchuk@...m.com>
Cc:     "tee-dev@...ts.linaro.org" <tee-dev@...ts.linaro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] optee: remove address tag in check_mem_type()

On Mon, Oct 12, 2020 at 11:26 AM Volodymyr Babchuk
<Volodymyr_Babchuk@...m.com> wrote:
>
> Before passing 'start' to find_vma() we need to remove
> tags from it to get sane results.
>
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@...m.com>
> ---
>  drivers/tee/optee/call.c | 2 ++
>  1 file changed, 2 insertions(+)

Would you mind giving a bit more background to this? For example in
which contexts this function does or doesn't work as expected? Do you
have any special use cases that don't work, etc? This is not a new
regression, it's rather a problem we've always had, right?

Thanks,
Jens

>
> diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
> index a5afbe6dee68..61420395137b 100644
> --- a/drivers/tee/optee/call.c
> +++ b/drivers/tee/optee/call.c
> @@ -562,6 +562,8 @@ static int check_mem_type(unsigned long start, size_t num_pages)
>         struct mm_struct *mm = current->mm;
>         int rc;
>
> +       start = untagged_addr(start);
> +
>         down_read(&mm->mmap_sem);
>         rc = __check_mem_type(find_vma(mm, start),
>                               start + num_pages * PAGE_SIZE);
> --
> 2.27.0