Re: [PATCH v13 18/20] tee/optee, arm64: untag user pointers in check_mem_type

Catalin Marinas
2019-03-22T16:22:23Z

On Wed, Mar 20, 2019 at 03:51:32PM +0100, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
>
> check_mem_type() uses provided user pointers for vma lookups (via
> __check_mem_type()), which can only by done with untagged pointers.
>
> Untag user pointers in this function.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> ---
> drivers/tee/optee/call.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
> index a5afbe6dee68..e3be20264092 100644
> --- a/drivers/tee/optee/call.c
> +++ b/drivers/tee/optee/call.c
> @@ -563,6 +563,7 @@ static int check_mem_type(unsigned long start, size_t num_pages)
> int rc;
>
> down_read(&mm->mmap_sem);
> + start = untagged_addr(start);
> rc = __check_mem_type(find_vma(mm, start),
> start + num_pages * PAGE_SIZE);
> up_read(&mm->mmap_sem);

I guess we could just untag this in tee_shm_register(). The tag is not
relevant to a TEE implementation (firmware) anyway.

--
Catalin