Re: rtlwifi: potential bugs

[Pkshih <pkshih@realtek.com>]

On Wed, 2021-05-05 at 16:20 +0200, Inigo Huguet wrote:
> If it's no problem to add them, a comment STARTING WITH
> `coverity[identical_branches]` should suppress the warnings.
> 
> Example:
> 
> /* Explanation why this code is fine
>  * and great
>  */
> /* coverity[identical_branches] */
> if (...)
>         ...
> 
> Thanks!
> 
> On Wed, May 5, 2021 at 4:03 PM Pkshih <pkshih@realtek.com> wrote:
> >
> > On Wed, 2021-05-05 at 13:01 +0000, Inigo Huguet wrote:
> > > Hi,
> > >
> > > Thanks for the info. Maybe we should consider adding some comments to
> > > clarify this? Other people might also think these are bugs...
> > >
> > > Regards,
> > >
> > > On Wed, May 5, 2021 at 2:13 PM Pkshih <pkshih@realtek.com> wrote:
> > > >
> > > > On Wed, 2021-05-05 at 11:23 +0000, Inigo Huguet wrote:
> > > > > On Fri, Apr 23, 2021 at 2:56 PM Inigo Huguet <ihuguet@redhat.com> wrote:
> > > > > >
> > > > > > Hello,
> > > > > >
> > > > > > Executing some static analysis on the kernel, we've got this results
> > > > > > affecting rtlwifi drivers:
> > > > > >
> > > > > > Error: IDENTICAL_BRANCHES (CWE-398): [#def212]
> > > > > > kernel-5.11.0-0.rc7.151/linux-5.11.0-0.rc7.151.el9.x86_64/drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8821a2ant.c:2813:
> > > > > > identical_branches: The same code is executed regardless of whether
> > > > > > "bt_rssi_state == BTC_RSSI_STATE_HIGH || bt_rssi_state ==
> > > > > > BTC_RSSI_STATE_STAY_HIGH" is true, because the 'then' and 'else'
> > > > > > branches are identical. Should one of the branches be modified, or the
> > > > > > entire 'if' statement replaced?
> > > > > > # 2811|   }
> > > > > > # 2812|
> > > > > > # 2813|-> if ((bt_rssi_state == BTC_RSSI_STATE_HIGH) ||
> > > > > > # 2814|      (bt_rssi_state == BTC_RSSI_STATE_STAY_HIGH)) {
> > > > > > # 2815|   btc8821a2ant_ps_tdma(btcoexist, NORMAL_EXEC, true, 23);
> > > > > >
> > > > > > Error: IDENTICAL_BRANCHES (CWE-398): [#def213]
> > > > > > kernel-5.11.0-0.rc7.151/linux-5.11.0-0.rc7.151.el9.x86_64/drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8821a2ant.c:2947:
> > > > > > identical_branches: The same code is executed regardless of whether
> > > > > > "bt_rssi_state == BTC_RSSI_STATE_HIGH || bt_rssi_state ==
> > > > > > BTC_RSSI_STATE_STAY_HIGH" is true, because the 'then' and 'else'
> > > > > > branches are identical. Should one of the branches be modified, or the
> > > > > > entire 'if' statement replaced?
> > > > > > # 2945|   }
> > > > > > # 2946|
> > > > > > # 2947|-> if ((bt_rssi_state == BTC_RSSI_STATE_HIGH) ||
> > > > > > # 2948|      (bt_rssi_state == BTC_RSSI_STATE_STAY_HIGH))
> > > > > > # 2949|   btc8821a2ant_ps_tdma(btcoexist, NORMAL_EXEC, true, 26);
> > > > > >
> > > > > > Error: IDENTICAL_BRANCHES (CWE-398): [#def214]
> > > > > > kernel-5.11.0-0.rc7.151/linux-5.11.0-0.rc7.151.el9.x86_64/drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8821a2ant.c:3135:
> > > > > > identical_branches: The same code is executed regardless of whether
> > > > > > "wifi_bw == BTC_WIFI_BW_LEGACY" is true, because the 'then' and 'else'
> > > > > > branches are identical. Should one of the branches be modified, or the
> > > > > > entire 'if' statement replaced?
> > > > > > # 3133|   btcoexist->btc_get(btcoexist, BTC_GET_U4_WIFI_BW, &wifi_bw);
> > > > > > # 3134|
> > > > > > # 3135|-> if (wifi_bw == BTC_WIFI_BW_LEGACY) {
> > > > > > # 3136|   /* for HID at 11b/g mode */
> > > > > > # 3137|   btc8821a2ant_coex_table(btcoexist, NORMAL_EXEC, 0x55ff55ff,
> > > > > >
> > > > > > Error: IDENTICAL_BRANCHES (CWE-398): [#def215]
> > > > > > kernel-5.11.0-0.rc7.151/linux-5.11.0-0.rc7.151.el9.x86_64/drivers/net/wireless/realtek/rtlwifi/btcoexist/halbtc8821a2ant.c:3324:
> > > > > > identical_branches: The same code is executed regardless of whether
> > > > > > "bt_rssi_state == BTC_RSSI_STATE_HIGH || bt_rssi_state ==
> > > > > > BTC_RSSI_STATE_STAY_HIGH" is true, because the 'then' and 'else'
> > > > > > branches are identical. Should one of the branches be modified, or the
> > > > > > entire 'if' statement replaced?
> > > > > > # 3322|   }
> > > > > > # 3323|
> > > > > > # 3324|-> if ((bt_rssi_state == BTC_RSSI_STATE_HIGH) ||
> > > > > > # 3325|      (bt_rssi_state == BTC_RSSI_STATE_STAY_HIGH)) {
> > > > > > # 3326|   btc8821a2ant_ps_tdma(btcoexist, NORMAL_EXEC, true, 23);
> > > > > >
> > > > > >
> > > > > > In my opinion, they seem to be real bugs. However, it's very difficult
> > > > > > to imagine what actions must be taken on each branch of the if-else
> > > > > > because they strongly depend on magic numbers, which are different
> > > > > > configurations for the hw, I guess.
> > > > > >
> > > > > > Can the maintainers confirm if these are real bugs and see how to fix them?
> > > > > >
> > > > > > Regards
> > > > > > --
> > > > > > Íñigo Huguet
> > > > >
> > > > > Hello,
> > > > >
> > > > > A few weeks ago I sent the message above notifying a potential bug in
> > > > > rtlwifi module. I just wanted to be sure that it has been received.
> > > > > Can the maintainers acknowledge whether they have seen it?
> > > > >
> > > >
> > > > Hi,
> > > >
> > > > Not real bugs. The coexistence programmers preserve the same code of
> > > > branches intentionally to fine tune performance easier, because bandwidth and
> > > > RSSI strength are highly related to coexistence performance.
> > > > The basic rule of performance tuning is to assign most time slot to BT
> > > > for realtime application, and WiFi uses remaining time slot but don't lower
> > > > than low bound.
> > > >
> > > >
> >
> > Hi,
> >
> > I can add comments. Do you need any keyword within comment to avoid your
> > checking tool warns this false alarm?
> >

I do "git grep coverity | wc -l" and there are only 8 instances.
I'm not sure if I can add comments with "coverity" marker.

--
Ping-Ke