linux-kernel - Re: [PATCH] scsi: gdth: Only call dma_free_coherent when buf is not NULL in ioc

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Date:   Wed, 20 Mar 2019 12:12:38 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Achim Leubner <achim_leubner@...ptec.com>
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] scsi: gdth: Only call dma_free_coherent when buf is not
 NULL in ioc_general

On Thu, Mar 07, 2019 at 04:18:39PM -0700, Nathan Chancellor wrote:
> When building with -Wsometimes-uninitialized, Clang warns:
> 
> drivers/scsi/gdth.c:3662:6: warning: variable 'paddr' is used
> uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
> 
> Don't attempt to call dma_free_coherent when buf is NULL (meaning that
> we never called dma_alloc_coherent and initialized paddr), which avoids
> this warning.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/402
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  drivers/scsi/gdth.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/gdth.c b/drivers/scsi/gdth.c
> index e7f1dd4f3b66..0ca9b4393770 100644
> --- a/drivers/scsi/gdth.c
> +++ b/drivers/scsi/gdth.c
> @@ -3697,8 +3697,9 @@ static int ioc_general(void __user *arg, char *cmnd)
>  
>  	rval = 0;
>  out_free_buf:
> -	dma_free_coherent(&ha->pdev->dev, gen.data_len + gen.sense_len, buf,
> -			paddr);
> +	if (buf)
> +		dma_free_coherent(&ha->pdev->dev, gen.data_len + gen.sense_len,
> +				  buf, paddr);
>  	return rval;
>  }
>   
> -- 
> 2.21.0
> 

Gentle ping (if there was a response to this, I didn't receive it). I
know I sent it in the middle of a merge window so I get if it slipped
through the cracks.

Thanks,
Nathan