[PATCH v2] common: avb_verify: prevent opening incorrect session

[Jens Wiklander]

On Mon, Jan 23, 2023 at 5:09 PM Ivan Khoronzhuk
<ivan.khoronzhuk at gmail.com> wrote:
>
> On Mon, Jan 23, 2023 at 04:34:33PM +0100, Jens Wiklander wrote:
> >On Mon, Jan 23, 2023 at 04:51:29PM +0200, Ivan Khoronzhuk wrote:
> >> The arg->session is not valid if arg->ret != NULL, so can't be
> >> assigned. Leave retry for just "ret" error to save same behaviour.
> >>
> >> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk at gmail.com>
> >> ---
> >>  common/avb_verify.c | 12 ++++++++----
> >>  1 file changed, 8 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/common/avb_verify.c b/common/avb_verify.c
> >> index 0520a71455..97451592f5 100644
> >> --- a/common/avb_verify.c
> >> +++ b/common/avb_verify.c
> >> @@ -619,10 +619,14 @@ static int get_open_session(struct AvbOpsData *ops_data)
> >>              memset(&arg, 0, sizeof(arg));
> >>              tee_optee_ta_uuid_to_octets(arg.uuid, &uuid);
> >>              rc = tee_open_session(tee, &arg, 0, NULL);
> >> -            if (!rc) {
> >> -                    ops_data->tee = tee;
> >> -                    ops_data->session = arg.session;
> >> -            }
> >> +            if (rc)
> >> +                    continue;
> >> +
> >> +            if (arg.ret)
> >> +                    return -EIO;
> >> +
> >> +            ops_data->tee = tee;
> >> +            ops_data->session = arg.session;
> >>      }
> >>
> >>      return 0;
> >
> >It looks like this function is still slightly broken. The function
> >should, if I understand it correctly, return usable tee and session
> >pointers on success, else return an error code. The unconditional return
> >0 at the end doesn't seem right.
> >
> >Thanks,
> >Jens
>
> It doesn't return, it loops infinitely...
> Yes, it looks so, but it's how it works. I don't see a reason why the
> function must loop trying to open the session that potentially never will be
> opened. But this is how it's implemented and I didn't wont to change this
> behaviour that can have some "sacral" roots, only add a fix I bother, I've

No worries, no need to be bug compatible here. :-)

> mentioned it in the comment. Better would be drop this loop ofc and add the
> following:
>
> +               if (ret || arg.ret)
> +                       return -EIO;

A loop is needed to find the TEE device. Right now I guess there's
only one and it will be found in the first round.

>
> I can do this in v3 if you don't mind.

Yes, please fix the function to return an error if a session can't be found.

Thanks,
Jens