linux-kernel - [media-dvb-usb-v2] question about value overwrite

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Date:   Thu, 18 May 2017 14:09:01 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Malcolm Priestley <tvboxspy@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [media-dvb-usb-v2] question about value overwrite


Hello everybody,

While looking into Coverity ID 1226934 I ran into the following piece  
of code at drivers/media/usb/dvb-usb-v2/lmedm04.c:205

205static int lme2510_stream_restart(struct dvb_usb_device *d)
206{
207        struct lme2510_state *st = d->priv;
208        u8 all_pids[] = LME_ALL_PIDS;
209        u8 stream_on[] = LME_ST_ON_W;
210        int ret;
211        u8 rbuff[1];
212        if (st->pid_off)
213                ret = lme2510_usb_talk(d, all_pids, sizeof(all_pids),
214                        rbuff, sizeof(rbuff));
215        /*Restart Stream Command*/
216        ret = lme2510_usb_talk(d, stream_on, sizeof(stream_on),
217                        rbuff, sizeof(rbuff));
218        return ret;
219}

The issue is that the value store in variable _ret_ at line 213 is  
overwritten by the one stored at line 216, before it can be used.

My question is if an _else_ statement is missing, or the variable  
assignment at line 213 should be removed, leaving just the call  
lme2510_usb_talk(d, all_pids, sizeof(all_pids), rbuff, sizeof(rbuff));  
in place.

Maybe either of the following patches could be applied:

index 924adfd..d573144 100644
--- a/drivers/media/usb/dvb-usb-v2/lmedm04.c
+++ b/drivers/media/usb/dvb-usb-v2/lmedm04.c
@@ -207,15 +207,15 @@ static int lme2510_stream_restart(struct  
dvb_usb_device *d)
         struct lme2510_state *st = d->priv;
         u8 all_pids[] = LME_ALL_PIDS;
         u8 stream_on[] = LME_ST_ON_W;
-       int ret;
         u8 rbuff[1];
+
         if (st->pid_off)
-               ret = lme2510_usb_talk(d, all_pids, sizeof(all_pids),
+               lme2510_usb_talk(d, all_pids, sizeof(all_pids),
                         rbuff, sizeof(rbuff));
+
         /*Restart Stream Command*/
-       ret = lme2510_usb_talk(d, stream_on, sizeof(stream_on),
+       return lme2510_usb_talk(d, stream_on, sizeof(stream_on),
                         rbuff, sizeof(rbuff));
-       return ret;
  }

index 924adfd..dd51f05 100644
--- a/drivers/media/usb/dvb-usb-v2/lmedm04.c
+++ b/drivers/media/usb/dvb-usb-v2/lmedm04.c
@@ -207,15 +207,15 @@ static int lme2510_stream_restart(struct  
dvb_usb_device *d)
         struct lme2510_state *st = d->priv;
         u8 all_pids[] = LME_ALL_PIDS;
         u8 stream_on[] = LME_ST_ON_W;
-       int ret;
         u8 rbuff[1];
+
         if (st->pid_off)
-               ret = lme2510_usb_talk(d, all_pids, sizeof(all_pids),
+               return lme2510_usb_talk(d, all_pids, sizeof(all_pids),
                         rbuff, sizeof(rbuff));
-       /*Restart Stream Command*/
-       ret = lme2510_usb_talk(d, stream_on, sizeof(stream_on),
+       else
+               /*Restart Stream Command*/
+               return lme2510_usb_talk(d, stream_on, sizeof(stream_on),
                         rbuff, sizeof(rbuff));
-       return ret;
  }

What do you think?

I'd really appreciate any comment on this.

Thank you!
--
Gustavo A. R. Silva