linux-kernel - Re: [PATCH] (powerpc/512) Fix possible `dma_unmap

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Message-ID: <878qm1wxfs.fsf@mpe.ellerman.id.au>
Date: Mon, 09 Jun 2025 10:49:59 +1000
From: Michael Ellerman <mpe@...erman.id.au>
To: Thomas Fourier <fourier.thomas@...il.com>
Cc: Thomas Fourier <fourier.thomas@...il.com>, Anatolij Gustschin
 <agust@...x.de>, Madhavan Srinivasan <maddy@...ux.ibm.com>, Nicholas
 Piggin <npiggin@...il.com>, Christophe Leroy
 <christophe.leroy@...roup.eu>, Uwe Kleine-König
 <u.kleine-koenig@...libre.com>, "open list:LINUX FOR POWERPC EMBEDDED
 MPC5XXX" <linuxppc-dev@...ts.ozlabs.org>, open list
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] (powerpc/512) Fix possible `dma_unmap_single()` on
 uninitialized pointer

Thomas Fourier <fourier.thomas@...il.com> writes:
> If the device configuration fails (if `dma_dev->device_config()`),
> `sg_dma_address(&sg)` is not initialized and the jump to `err_dma_prep`
> leads to calling `dma_unmap_single()` on `sg_dma_address(&sg)`.
>
> Signed-off-by: Thomas Fourier <fourier.thomas@...il.com>
> ---
>  arch/powerpc/platforms/512x/mpc512x_lpbfifo.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/platforms/512x/mpc512x_lpbfifo.c b/arch/powerpc/platforms/512x/mpc512x_lpbfifo.c
> index 9668b052cd4b..ef3be438f914 100644
> --- a/arch/powerpc/platforms/512x/mpc512x_lpbfifo.c
> +++ b/arch/powerpc/platforms/512x/mpc512x_lpbfifo.c
> @@ -241,8 +241,7 @@ static int mpc512x_lpbfifo_kick(void)
>  
>  	/* Make DMA channel work with LPB FIFO data register */
>  	if (dma_dev->device_config(lpbfifo.chan, &dma_conf)) {
> -		ret = -EINVAL;
> -		goto err_dma_prep;
> +		return -EINVAL;
>  	}
>  
>  	sg_init_table(&sg, 1);

Yep looks good. That's the first use of goto for error handling, and
it's clearly too early. All the previous error cases do a direct return.

Reviewed-by: Michael Ellerman <mpe@...erman.id.au>

cheers