Messages in this thread | | | Date | Wed, 24 Apr 2013 18:00:28 +0400 | From | Sergei Shtylyov <> | Subject | Re: [PATCH 04/10] usb: musb: ux500: harden checks for platform data |
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Hello.
On 24-04-2013 10:53, Lee Jones wrote:
>>> struct musb_hdrc_platform_data *plat = dev->platform_data; >>> - struct ux500_musb_board_data *data = plat->board_data; >>> + struct ux500_musb_board_data *data;
>>> - param_array = data->dma_rx_param_array; >>> + param_array = (data) ? data->dma_rx_param_array : NULL;
>> Why enclose a simple variable in parens?
> Because 'data' is a pointer, so it contains a memory location,
Pointer points to memory location, not contains it.
> but if > 'plat->board_data' is NULL, then 'data' will be NULL (essentially > memory location 0x00000000).
So what?
> So if we were to read-in to 'struct ux500_musb_board_data *data', by > index 'dma_rx_param_array', which I believe is '0' in this case:
> struct ux500_musb_board_data { > void **dma_rx_param_array; > void **dma_tx_param_array; > bool (*dma_filter)(struct dma_chan *chan, void *filter_param); > };
> ... then we're saying take the data from this memory location:
> param_array = *((0x00000000)->(0x0));
> Which will cause a kernel Oops, due to the fact that address 0x0 isn't > allocated to us, so you get something like:
> "Unable to handle kernel NULL pointer dereference at virtual address 00000000"
We're not dereferencing 'data', so I completely fail to follow you.
> Hope that helps.
Not at all.
> Kind regards, > Lee
WBR, Sergei
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