Re: [PATCH V2] staging: gpib: Remove a dead condition in if statement

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Oct 16, 2024 at 01:53:18AM -0600, Everest K.C. wrote:
> The variable `residue` is an unsigned int, also the function
> `fluke_get_dma_residue` returns an unsigned int. The value of
> an unsigned int can only be 0 at minimum.
> The less-than-zero comparison can never be true.
> Fix it by removing the dead condition in the if statement.
> 
> This issue was reported by Coverity Scan.
> Report:
> CID 1600782: (#1 of 1): Macro compares unsigned to 0 (NO_EFFECT)
> unsigned_compare: This less-than-zero comparison of an unsigned value
> is never true. residue < 0U.
> 
> Signed-off-by: Everest K.C. <everestkc@everestkc.com.np>
> ---
> V1 -> V2: - Fixed typo of comparison in changelog
>           - Removed Fixes tag 
> 
>  drivers/staging/gpib/eastwood/fluke_gpib.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/gpib/eastwood/fluke_gpib.c b/drivers/staging/gpib/eastwood/fluke_gpib.c
> index f9f149db222d..51b4f9891a34 100644
> --- a/drivers/staging/gpib/eastwood/fluke_gpib.c
> +++ b/drivers/staging/gpib/eastwood/fluke_gpib.c
> @@ -644,7 +644,7 @@ static int fluke_dma_read(gpib_board_t *board, uint8_t *buffer,
>  	 */
>  	usleep_range(10, 15);
>  	residue = fluke_get_dma_residue(e_priv->dma_channel, dma_cookie);
> -	if (WARN_ON_ONCE(residue > length || residue < 0))
> +	if (WARN_ON_ONCE(residue > length))

No, this is incorrect, now we never notice is the call to
fluke_get_dma_residue() has failed.  Please fix that bug instead (hint,
Covertity is giving you a pointer to where something might be wrong, but
this change is NOT how to fix it.)

thanks,

greg k-h