linux-kernel - Re: [PATCH] serial: tegra: Fix memory leak on DMA setup failure

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Date:	Wed, 20 May 2015 12:25:44 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Alexandre Courbot <acourbot@...dia.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Jiri Slaby" <jslaby@...e.cz>
CC:	<linux-serial@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] serial: tegra: Fix memory leak on DMA setup failure


On 20/05/15 12:21, Jon Hunter wrote:
> If the call to dmaengine_slave_config() fails, then the DMA buffer will
> not be freed/unmapped. Fix this by moving the code that stores the
> address of the buffer in the tegra_uart_port structure to before the
> call to dmaengine_slave_config().

By the way, just to be clear, I did try to fix this before [1], but
failed :-(

Thanks to Alex for pointing this out.

Cheers
Jon

[1] https://lkml.org/lkml/2015/5/5/802

> Reported-by: Alexandre Courbot <acourbot@...dia.com>
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> ---
>  drivers/tty/serial/serial-tegra.c | 32 +++++++++++---------------------
>  1 file changed, 11 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
> index 3b63f103f0c9..cf0133ae762d 100644
> --- a/drivers/tty/serial/serial-tegra.c
> +++ b/drivers/tty/serial/serial-tegra.c
> @@ -999,6 +999,12 @@ static int tegra_uart_dma_channel_allocate(struct tegra_uart_port *tup,
>  			dma_release_channel(dma_chan);
>  			return -ENOMEM;
>  		}
> +		dma_sconfig.src_addr = tup->uport.mapbase;
> +		dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> +		dma_sconfig.src_maxburst = 4;
> +		tup->rx_dma_chan = dma_chan;
> +		tup->rx_dma_buf_virt = dma_buf;
> +		tup->rx_dma_buf_phys = dma_phys;
>  	} else {
>  		dma_phys = dma_map_single(tup->uport.dev,
>  			tup->uport.state->xmit.buf, UART_XMIT_SIZE,
> @@ -1009,39 +1015,23 @@ static int tegra_uart_dma_channel_allocate(struct tegra_uart_port *tup,
>  			return -ENOMEM;
>  		}
>  		dma_buf = tup->uport.state->xmit.buf;
> -	}
> -
> -	if (dma_to_memory) {
> -		dma_sconfig.src_addr = tup->uport.mapbase;
> -		dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
> -		dma_sconfig.src_maxburst = 4;
> -	} else {
>  		dma_sconfig.dst_addr = tup->uport.mapbase;
>  		dma_sconfig.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
>  		dma_sconfig.dst_maxburst = 16;
> +		tup->tx_dma_chan = dma_chan;
> +		tup->tx_dma_buf_virt = dma_buf;
> +		tup->tx_dma_buf_phys = dma_phys;
>  	}
>  
>  	ret = dmaengine_slave_config(dma_chan, &dma_sconfig);
>  	if (ret < 0) {
>  		dev_err(tup->uport.dev,
>  			"Dma slave config failed, err = %d\n", ret);
> -		goto scrub;
> +		tegra_uart_dma_channel_free(tup, dma_to_memory);
> +		return ret;
>  	}
>  
> -	if (dma_to_memory) {
> -		tup->rx_dma_chan = dma_chan;
> -		tup->rx_dma_buf_virt = dma_buf;
> -		tup->rx_dma_buf_phys = dma_phys;
> -	} else {
> -		tup->tx_dma_chan = dma_chan;
> -		tup->tx_dma_buf_virt = dma_buf;
> -		tup->tx_dma_buf_phys = dma_phys;
> -	}
>  	return 0;
> -
> -scrub:
> -	tegra_uart_dma_channel_free(tup, dma_to_memory);
> -	return ret;
>  }
>  
>  static int tegra_uart_startup(struct uart_port *u)
> 
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