linux-kernel - Re: [PATCH v4] usb-storage: Check whether the media is initialized successfully

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Date: Sat, 25 May 2024 09:32:30 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Shichao Lai <shichaorai@...il.com>
Cc: gregkh@...uxfoundation.org, oneukum@...e.com, linux-usb@...r.kernel.org,
  usb-storage@...ts.one-eyed-alien.net, linux-kernel@...r.kernel.org,
  xingwei lee <xrivendell7@...il.com>, yue sun <samsun1006219@...il.com>
Subject: Re: [PATCH v4] usb-storage: Check whether the media is initialized
 successfully

On Sat, May 25, 2024 at 02:36:53PM +0800, Shichao Lai wrote:
> The member "uzonesize" of struct alauda_info will remain 0
> if alauda_init_media() fails, potentially causing divide errors
> in alauda_read_data() and alauda_write_lba().
> - Add a member "initialized" to struct alauda_info as a symbol
>   for media initialization.
> - Change a condition in alauda_check_media() to ensure the
>   first initialization.
> - Add an error check for the return value of alauda_init_media().
> 
> Reported-by: xingwei lee <xrivendell7@...il.com>
> Reported-by: yue sun <samsun1006219@...il.com>
> Suggested-by: Oliver Neukum <oneukum@...e.com>

Oliver did not suggest that the patch be written this way.

> Signed-off-by: Shichao Lai <shichaorai@...il.com>
> ---
> Changes since v1:
> - Check the initialization of alauda_check_media() 
>   which is the root cause.
> 
>  drivers/usb/storage/alauda.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/storage/alauda.c b/drivers/usb/storage/alauda.c
> index 115f05a6201a..ddf0da203481 100644
> --- a/drivers/usb/storage/alauda.c
> +++ b/drivers/usb/storage/alauda.c
> @@ -105,6 +105,8 @@ struct alauda_info {
>  	unsigned char sense_key;
>  	unsigned long sense_asc;	/* additional sense code */
>  	unsigned long sense_ascq;	/* additional sense code qualifier */
> +
> +	bool initialized;           /* true if the media is initialized */

Now with the patch written out, I think a better name for this variable 
would be media_initialized.  That is a better description of what it 
means (it doesn't mean that the driver or the device is initialized).  
And then you could remove the comment, because it would be obvious.

>  };
>  
>  #define short_pack(lsb,msb) ( ((u16)(lsb)) | ( ((u16)(msb))<<8 ) )
> @@ -476,11 +478,12 @@ static int alauda_check_media(struct us_data *us)
>  	}
>  
>  	/* Check for media change */
> -	if (status[0] & 0x08) {
> +	if (status[0] & 0x08 || !info->initialized) {
>  		usb_stor_dbg(us, "Media change detected\n");
>  		alauda_free_maps(&MEDIA_INFO(us));
> -		alauda_init_media(us);
> -
> +		rc = alauda_init_media(us);
> +		if (rc == USB_STOR_TRANSPORT_GOOD)
> +			info->initialized = true;
>  		info->sense_key = UNIT_ATTENTION;
>  		info->sense_asc = 0x28;
>  		info->sense_ascq = 0x00;
> @@ -1120,6 +1123,7 @@ static int init_alauda(struct us_data *us)
>  	info->wr_ep = usb_sndbulkpipe(us->pusb_dev,
>  		altsetting->endpoint[0].desc.bEndpointAddress
>  		& USB_ENDPOINT_NUMBER_MASK);
> +	info->initialized = false;

You don't need to do this.  The info pointer is an alias for us->extra, 
which is allocated by kzalloc(), which clears all the memory it 
allocates to zero.

Alan Stern