linux-kernel - Re: drivers/net/usb/pegasus.c:461:2: warning: Value stored to 'ret' is never read [clang-analyzer-deadcode.DeadStores]

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <538445a9-3f96-5099-fb83-517e756a93fa@gmail.com>
Date:   Mon, 9 Aug 2021 23:37:08 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     kernel test robot <rong.a.chen@...el.com>,
        clang-built-linux@...glegroups.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: drivers/net/usb/pegasus.c:461:2: warning: Value stored to 'ret'
 is never read [clang-analyzer-deadcode.DeadStores]

On 8/9/21 9:36 PM, Petko Manolov wrote:
> On 21-08-09 14:06:11, Pavel Skripkin wrote:
>> On 8/9/21 1:37 PM, kernel test robot wrote:
>> > 
>> > tree:
>> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> > head:   85a90500f9a1717c4e142ce92e6c1cb1a339ec78
>> > commit: 8a160e2e9aeb8318159b48701ad8a6e22274372d net: usb: pegasus:
>> > Check the return value of get_geristers() and friends;
>> > date:   4 days ago
>> > :::::: branch date: 8 hours ago
>> > :::::: commit date: 4 days ago
>> > config: x86_64-randconfig-c001-20210808 (attached as .config)
>> > compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project
>> > 41a6b50c25961addc04438b567ee1f4ef9e40f98)
>> > reproduce (this is a W=1 build):
>> >           wget
>> > https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross
>> > -O ~/bin/make.cross
>> >           chmod +x ~/bin/make.cross
>> >           # install x86_64 cross compiling tool for clang build
>> >           # apt-get install binutils-x86-64-linux-gnu
>> >           #
>> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8a160e2e9aeb8318159b48701ad8a6e22274372d
>> >           git remote add linus
>> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>> >           git fetch --no-tags linus master
>> >           git checkout 8a160e2e9aeb8318159b48701ad8a6e22274372d
>> >           # save the attached .config to linux build tree
>> >           COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross
>> > ARCH=x86_64 clang-analyzer
>> > If you fix the issue, kindly add following tag as appropriate
>> > Reported-by: kernel test robot <lkp@...el.com>
>> 
>> Hi, @Petko!
>> 
>> For you not to scan all these warnings:
>> 
>> > > > drivers/net/usb/pegasus.c:461:2: warning: Value stored to 'ret' is never read [clang-analyzer-deadcode.DeadStores]
>> >              ret = set_registers(pegasus, EthCtrl0, 3, data);
>> >              ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> >      drivers/net/usb/pegasus.c:461:2: note: Value stored to 'ret' is
>> > never read
>> >              ret = set_registers(pegasus, EthCtrl0, 3, data);
>> >              ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> 
>> This is the real bug, I think. Can be fixed like this:
>> 
>> diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c
>> index 22353bab76c8..f2b8891c7b36 100644
>> --- a/drivers/net/usb/pegasus.c
>> +++ b/drivers/net/usb/pegasus.c
>> @@ -459,6 +459,8 @@ static int enable_net_traffic(struct net_device *dev,
>> struct usb_device *usb)
>> 
>>  	memcpy(pegasus->eth_regs, data, sizeof(data));
>>  	ret = set_registers(pegasus, EthCtrl0, 3, data);
>> +	if (ret < 0)
>> +		goto fail;
>> 
>>  	if (usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS ||
>>  	    usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS2 ||
>> 
>> 
>> It was caused by our last refactoring: enable_net_traffic() now returns 0 on
>> success and this ret is never checked.
> 
> I'd rather remove the 'ret = ' part and leave set_registers() alone.  If this
> particular write operation fail, it doesn't mean the adapter won't work at all.
> Perhaps it won't be the most optimal mode, but it will work.  There are some
> legal checks after set_registers() that also make sense to pass.  So the patch i
> suggest looks like:
> 
> 
> diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c
> index 652e9fcf0b77..49cfc720d78f 100644
> --- a/drivers/net/usb/pegasus.c
> +++ b/drivers/net/usb/pegasus.c
> @@ -433,7 +433,7 @@ static int enable_net_traffic(struct net_device *dev, struct usb_device *usb)
>          data[2] = loopback ? 0x09 : 0x01;
> 
>          memcpy(pegasus->eth_regs, data, sizeof(data));
> -       ret = set_registers(pegasus, EthCtrl0, 3, data);
> +       set_registers(pegasus, EthCtrl0, 3, data);
> 
>          if (usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS ||
>              usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS2 ||
> 

It works. I am not aware of device specifics, so I decided to handle the 
error instead of ignoring.

Will you take care of posting this patch, or I can do it with 
Suggested-by tag?



With regards,
Pavel Skripkin