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SubjectRe: [PATCH] Bluetooth: Simplify / fix return values from tk_request
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On 4/3/20 8:13 AM, Alain Michaud wrote:
> Hi Guenter/Marcel,
>
>
> On Fri, Apr 3, 2020 at 11:03 AM Guenter Roeck <linux@roeck-us.net> wrote:
>>
>> 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@chromium.org>
>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>> ---
>> 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.

Guenter

>> set_bit(SMP_FLAG_WAIT_USER, &smp->flags);
>> return 0;
>> }
>> --
>> 2.17.1
>>
>
> Thanks,
> Alain
>

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