RE: Coverity: rswitch_gwca_queue_alloc_skb(): Control flow issues

[Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>]

Hello!

> From: coverity-bot, Sent: Saturday, November 5, 2022 4:30 AM
> 
> Hello!
> 
> This is an experimental semi-automated report about issues detected by
> Coverity from a scan of next-20221104 as part of the linux-next scan project:
<snip>
> 
> You're getting this email because you were associated with the identified
> lines of code (noted below) that were touched by commits:
> 
>   Wed Nov 2 12:38:53 2022 +0000
>     3590918b5d07 ("net: ethernet: renesas: Add support for "Ethernet Switch"")
> 
> Coverity reported the following:
> 
> *** CID 1527147:  Control flow issues  (NO_EFFECT)
> drivers/net/ethernet/renesas/rswitch.c:270 in rswitch_gwca_queue_alloc_skb()
> 264     			goto err;
> 265     	}
> 266
> 267     	return 0;
> 268
> 269     err:
> vvv     CID 1527147:  Control flow issues  (NO_EFFECT)
> vvv     This greater-than-or-equal-to-zero comparison of an unsigned value is always true. "i >= 0U".
> 270     	for (i--; i >= 0; i--) {
> 271     		index = (i + start_index) % gq->ring_size;
> 272     		dev_kfree_skb(gq->skbs[index]);
> 273     		gq->skbs[index] = NULL;
> 274     	}
> 275
> 
> If this is a false positive, please let us know so we can mark it as
> such, or teach the Coverity rules to be smarter. If not, please make
> sure fixes get into linux-next. :) For patches fixing this, please
> include these lines (but double-check the "Fixes" first):

Thank you for the report! I should fix the driver. 
I also realized that rswitch_gwca_queue_ts_fill() has the same issue.

Best regards,
Yoshihiro Shimoda

> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> Addresses-Coverity-ID: 1527147 ("Control flow issues")
> Fixes: 3590918b5d07 ("net: ethernet: renesas: Add support for "Ethernet Switch"")
> 
> Thanks for your attention!
> 
> --
> Coverity-bot