linux-kernel - Re: [PATCH 4.19 237/276] scsi: lpfc: avoid uninitialized variable warning

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Date:   Thu, 6 Jun 2019 18:53:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Pavel Machek <pavel@...x.de>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        James Smart <james.smart@...adcom.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 237/276] scsi: lpfc: avoid uninitialized variable
 warning

On Thu, Jun 06, 2019 at 09:00:42AM -0700, Nathan Chancellor wrote:
> On Thu, Jun 06, 2019 at 02:53:23PM +0200, Pavel Machek wrote:
> > Hi!
> > 
> > > [ Upstream commit faf5a744f4f8d76e7c03912b5cd381ac8045f6ec ]
> > > 
> > > clang -Wuninitialized incorrectly sees a variable being used without
> > > initialization:
> > > 
> > > drivers/scsi/lpfc/lpfc_nvme.c:2102:37: error: variable 'localport' is uninitialized when used here
> > >       [-Werror,-Wuninitialized]
> > >                 lport = (struct lpfc_nvme_lport *)localport->private;
> > >                                                   ^~~~~~~~~
> > > drivers/scsi/lpfc/lpfc_nvme.c:2059:38: note: initialize the variable 'localport' to silence this warning
> > >         struct nvme_fc_local_port *localport;
> > >                                             ^
> > >                                              = NULL
> > > 1 error generated.
> > > 
> > > This is clearly in dead code, as the condition leading up to it is always
> > > false when CONFIG_NVME_FC is disabled, and the variable is always
> > > initialized when nvme_fc_register_localport() got called successfully.
> > > 
> > > Change the preprocessor conditional to the equivalent C construct, which
> > > makes the code more readable and gets rid of the warning.
> > 
> > Unfortunately, this missed "else" branch where the code was freeing
> > the memory with kfree(cstat)... so this introduces a memory leak.
> > 
> > Best regards,
> > 									Pavel
> 
> For the record, this is not a problem with the upstream commit (not
> saying you thought that or not, I just want to be clear).
> 
> Looks like commit 4c47efc140fa ("scsi: lpfc: Move SCSI and NVME Stats to
> hardware queue structures") "resolved" this by not making it an issue in
> the first place. I think the simpler fix is this.
> 
> Thanks for pointing it out!
> 
> diff --git a/drivers/scsi/lpfc/lpfc_nvme.c b/drivers/scsi/lpfc/lpfc_nvme.c
> index 099f70798fdd..645ffb5332b4 100644
> --- a/drivers/scsi/lpfc/lpfc_nvme.c
> +++ b/drivers/scsi/lpfc/lpfc_nvme.c
> @@ -2477,14 +2477,14 @@ lpfc_nvme_create_localport(struct lpfc_vport *vport)
>         lpfc_nvme_template.max_sgl_segments = phba->cfg_nvme_seg_cnt + 1;
>         lpfc_nvme_template.max_hw_queues = phba->cfg_nvme_io_channel;
>  
> +       if (!IS_ENABLED(CONFIG_NVME_FC))
> +               return ret;
> +
>         cstat = kmalloc((sizeof(struct lpfc_nvme_ctrl_stat) *
>                         phba->cfg_nvme_io_channel), GFP_KERNEL);
>         if (!cstat)
>                 return -ENOMEM;
>  
> -       if (!IS_ENABLED(CONFIG_NVME_FC))
> -               return ret;
> -
>         /* localport is allocated from the stack, but the registration
>          * call allocates heap memory as well as the private area.
>          */
> 

Can you send this as a real patch that I can queue up?

thanks,

greg k-h