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Subject: Re: [PATCH 120/190] Revert "tty: atmel_serial: fix a potential NULL
 pointer dereference"
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc:     Kangjie Lu <kjlu@umn.edu>,
        Richard Genoud <richard.genoud@gmail.com>,
        stable <stable@vger.kernel.org>
References: <20210421130105.1226686-1-gregkh@linuxfoundation.org>
 <20210421130105.1226686-121-gregkh@linuxfoundation.org>
From:   Jiri Slaby <jirislaby@kernel.org>
Message-ID: <57f44dfa-a502-ee4f-6d53-0ab7cba00e1b@kernel.org>
Date:   Thu, 22 Apr 2021 07:18:18 +0200
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On 21. 04. 21, 14:59, Greg Kroah-Hartman wrote:
> This reverts commit c85be041065c0be8bc48eda4c45e0319caf1d0e5.
> 
> Commits from @umn.edu addresses have been found to be submitted in "bad
> faith" to try to test the kernel community's ability to review "known
> malicious" changes.  The result of these submissions can be found in a
> paper published at the 42nd IEEE Symposium on Security and Privacy
> entitled, "Open Source Insecurity: Stealthily Introducing
> Vulnerabilities via Hypocrite Commits" written by Qiushi Wu (University
> of Minnesota) and Kangjie Lu (University of Minnesota).
> 
> Because of this, all submissions from this group must be reverted from
> the kernel tree and will need to be re-reviewed again to determine if
> they actually are a valid fix.  Until that work is complete, remove this
> change to ensure that no problems are being introduced into the
> codebase.
> 
> Cc: Kangjie Lu <kjlu@umn.edu>
> Cc: Richard Genoud <richard.genoud@gmail.com>
> Cc: stable <stable@vger.kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>   drivers/tty/serial/atmel_serial.c | 4 ----
>   1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index a24e5c2b30bc..9786d8e5f04f 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -1256,10 +1256,6 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
>   					 sg_dma_len(&atmel_port->sg_rx)/2,
>   					 DMA_DEV_TO_MEM,
>   					 DMA_PREP_INTERRUPT);
> -	if (!desc) {
> -		dev_err(port->dev, "Preparing DMA cyclic failed\n");
> -		goto chan_err;
> -	}

I cannot find anything malicious in the original fix:
* port->dev is valid for dev_err
* dmaengine_prep_dma_cyclic returns NULL in case of error
* chan_err invokes atmel_release_rx_dma which undoes the previous 
initialization code.

Hence a NACK from me for the revert.

>   	desc->callback = atmel_complete_rx_dma;
>   	desc->callback_param = port;
>   	atmel_port->desc_rx = desc;
> 


-- 
js
suse labs