netdev - Re: [PATCH v3] net: ethernet: ravb: exit if re-initialization fails in tx timeout

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Date:   Wed, 22 Jul 2020 11:18:34 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        davem@...emloft.net, kuba@...nel.org
Cc:     dirk.behme@...bosch.com, Shashikant.Suguni@...bosch.com,
        netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v3] net: ethernet: ravb: exit if re-initialization fails
 in tx timeout

On 21.07.2020 9:23, Yoshihiro Shimoda wrote:

> According to the report of [1], this driver is possible to cause
> the following error in ravb_tx_timeout_work().
> 
> ravb e6800000.ethernet ethernet: failed to switch device to config mode
> 
> This error means that the hardware could not change the state
> from "Operation" to "Configuration" while some tx and/or rx queue
> are operating. After that, ravb_config() in ravb_dmac_init() will fail,
> and then any descriptors will be not allocaled anymore so that NULL
> pointer dereference happens after that on ravb_start_xmit().
> 
> To fix the issue, the ravb_tx_timeout_work() should check
> the return values of ravb_stop_dma() and ravb_dmac_init().
> If ravb_stop_dma() fails, ravb_tx_timeout_work() re-enables TX and RX
> and just exits. If ravb_dmac_init() fails, just exits.
> 
> [1]
> https://lore.kernel.org/linux-renesas-soc/20200518045452.2390-1-dirk.behme@de.bosch.com/
> 
> Reported-by: Dirk Behme <dirk.behme@...bosch.com>
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> Reviewed-by: Sergei Shtylyov <sergei.shtylyov@...il.com>

    ACK, this tag is still good for v3.

> ---
>   Changes from RFC v2:
>   - Check the return value of ravb_init_dmac() too.
>   - Update the subject and description.
>   - Fix the comment in the code.
>   - Add Reviewed-by Sergei.
>   https://patchwork.kernel.org/patch/11673621/
> 
>   Changes from RFC v1:
>   - Check the return value of ravb_stop_dma() and exit if the hardware
>     condition can not be initialized in the tx timeout.
>   - Update the commit subject and description.
>   - Fix some typo.
>   https://patchwork.kernel.org/patch/11570217/
> 
>   Unfortunately, I still didn't reproduce the issue yet. But,
>   I got review from Sergei in v2. So, I removed RFC on this patch.

    Sorry for the sloppy code. :-|

MBR, Sergei