Re: [PATCH] Bluetooth: Simplify / fix return values from tk_request

[Sonny Sasaka]

Hi Marcel,

Can this patch be merged? Or do you prefer reverting the original
patch and relanding it together with the fix?

On Mon, Apr 6, 2020 at 5:06 AM Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
>
> Hi Guenter,
>
> >>> Some static checker run by 0day reports a variableScope warning.
> >>>
> >>> net/bluetooth/smp.c:870:6: warning:
> >>>        The scope of the variable 'err' can be reduced. [variableScope]
> >>>
> >>> There is no need for two separate variables holding return values.
> >>> Stick with the existing variable. While at it, don't pre-initialize
> >>> 'ret' because it is set in each code path.
> >>>
> >>> tk_request() is supposed to return a negative error code on errors,
> >>> not a bluetooth return code. The calling code converts the return
> >>> value to SMP_UNSPECIFIED if needed.
> >>>
> >>> Fixes: 92516cd97fd4 ("Bluetooth: Always request for user confirmation for Just Works")
> >>> Cc: Sonny Sasaka <sonnysasaka@xxxxxxxxxxxx>
> >>> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> >>> ---
> >>> net/bluetooth/smp.c | 9 ++++-----
> >>> 1 file changed, 4 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
> >>> index d0b695ee49f6..30e8626dd553 100644
> >>> --- a/net/bluetooth/smp.c
> >>> +++ b/net/bluetooth/smp.c
> >>> @@ -854,8 +854,7 @@ static int tk_request(struct l2cap_conn *conn, u8 remote_oob, u8 auth,
> >>>        struct l2cap_chan *chan = conn->smp;
> >>>        struct smp_chan *smp = chan->data;
> >>>        u32 passkey = 0;
> >>> -       int ret = 0;
> >>> -       int err;
> >>> +       int ret;
> >>>
> >>>        /* Initialize key for JUST WORKS */
> >>>        memset(smp->tk, 0, sizeof(smp->tk));
> >>> @@ -887,12 +886,12 @@ static int tk_request(struct l2cap_conn *conn, u8 remote_oob, u8 auth,
> >>>        /* If Just Works, Continue with Zero TK and ask user-space for
> >>>         * confirmation */
> >>>        if (smp->method == JUST_WORKS) {
> >>> -               err = mgmt_user_confirm_request(hcon->hdev, &hcon->dst,
> >>> +               ret = mgmt_user_confirm_request(hcon->hdev, &hcon->dst,
> >>>                                                hcon->type,
> >>>                                                hcon->dst_type,
> >>>                                                passkey, 1);
> >>> -               if (err)
> >>> -                       return SMP_UNSPECIFIED;
> >>> +               if (ret)
> >>> +                       return ret;
> >> I think there may be some miss match between expected types of error
> >> codes here.  The SMP error code type seems to be expected throughout
> >> this code base, so this change would propagate a potential negative
> >> value while the rest of the SMP protocol expects strictly positive
> >> error codes.
> >>
> >
> > Up to the patch introducing the SMP_UNSPECIFIED return value, tk_request()
> > returned negative error codes, and all callers convert it to SMP_UNSPECIFIED.
> >
> > If tk_request() is supposed to return SMP_UNSPECIFIED on error, it should
> > be returned consistently, and its callers don't have to convert it again.
>
> maybe we need to fix that initial patch then.
>
> Regards
>
> Marcel
>