linux-kernel - Re: [PATCH] i2c: aspeed: Avoid accessing freed buffers during i2c transfers.

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Message-ID: <20230805101004.dknxj7nqrt2aes5n@intel.intel>
Date:   Sat, 5 Aug 2023 12:10:04 +0200
From:   Andi Shyti <andi.shyti@...nel.org>
To:     Lixue Liang <lianglixuehao@....com>
Cc:     brendan.higgins@...ux.dev, benh@...nel.crashing.org,
        joel@....id.au, Lixue Liang <lianglixue@...atwall.com.cn>,
        linux-aspeed@...ts.ozlabs.org, openbmc@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        p.zabel@...gutronix.de, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] i2c: aspeed: Avoid accessing freed buffers during i2c
 transfers.

Hi Lixue,

On Fri, Jul 28, 2023 at 12:24:16PM +0000, Lixue Liang wrote:
> From: Lixue Liang <lianglixue@...atwall.com.cn>
> 
> After waiting for the transmission timeout, the I2C controller will
> continue to transmit data when the bus is idle. Clearing bus->msg will
> avoid kernel panic when accessing the freed msg->buf in
> aspeed_i2c_master_irq.

actually in aspeed_i2c_master_irq() you are already checking for
!bus->msgs.

What kind of panic are you referring to?

Andi

> Signed-off-by: Lixue Liang <lianglixue@...atwall.com.cn>
> ---
>  drivers/i2c/busses/i2c-aspeed.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index 2e5acfeb76c8..c83057497e26 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -713,6 +713,8 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
>  		spin_lock_irqsave(&bus->lock, flags);
>  		if (bus->master_state == ASPEED_I2C_MASTER_PENDING)
>  			bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
> +
> +		bus->msgs = NULL;
>  		spin_unlock_irqrestore(&bus->lock, flags);
>  
>  		return -ETIMEDOUT;
> -- 
> 2.27.0
>