linux-kernel - net: ethernet: starfire: while loop that is never executed

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Message-ID: <cf40ac34-1655-4eee-85dc-c836e77eb301@gmail.com>
Date: Tue, 29 Oct 2024 22:02:41 +0000
From: "Colin King (gmail)" <colin.i.king@...il.com>
To: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: net: ethernet: starfire: while loop that is never executed

Hi,

There is a while-loop in function set_vlan_mode in source 
drivers/net/ethernet/adaptec/starfire.c that currently never gets 
executed, the code is as follows:

         for_each_set_bit(vid, np->active_vlans, VLAN_N_VID) {
                 if (vlan_count == 32)
                         break;
                 writew(vid, filter_addr);
                 filter_addr += 16;
                 vlan_count++;
         }
         if (vlan_count == 32) {
                 ret |= PerfectFilterVlan;
                 while (vlan_count < 32) {
                         writew(0, filter_addr);
                         filter_addr += 16;
                         vlan_count++;
                 }
         }
         return ret;

the while (vlan_count < 32) loop will never get executed because the 
outer if statement is only executed if val_count is equal to 32 hence 
val_count < 32 will be false. I'm assuming the while loop is filing the 
unused slots with zero, so I suspect the code should be:

          if (vlan_count == 32)
                 ret |= PerfectFilterVlan;

          while (vlan_count < 32) {
                 writew(0, filter_addr);
                 filter_addr += 16;
                 vlan_count++;
          }

..however I can't find any info on this H/W and I can't test it, so I'm 
not confident my assumption here is correct.

Colin