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SubjectRe: [bug report] Input: add st-keyscan driver
On Tue, Jan 22, 2019 at 1:53 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> Hello Gabriel FERNANDEZ,

Hello Dan,

I have added CCs for the maintainers as well as Gabriel Fernandez as
currently you just have the linux-input mailing list

> The patch 062589b13991: "Input: add st-keyscan driver" from Apr 12,
> 2014, leads to the following static checker warning:
>
> drivers/input/keyboard/st-keyscan.c:156 keyscan_probe()
> error: potential zalloc NULL dereference: 'keypad_data->input_dev'
>
> drivers/input/keyboard/st-keyscan.c
> 125 static int keyscan_probe(struct platform_device *pdev)
> 126 {
> 127 struct st_keyscan *keypad_data;
> 128 struct input_dev *input_dev;
> 129 struct resource *res;
> 130 int error;
> 131
> 132 if (!pdev->dev.of_node) {
> 133 dev_err(&pdev->dev, "no DT data present\n");
> 134 return -EINVAL;
> 135 }
> 136
> 137 keypad_data = devm_kzalloc(&pdev->dev, sizeof(*keypad_data),
> 138 GFP_KERNEL);
> 139 if (!keypad_data)
> 140 return -ENOMEM;
> 141
> 142 input_dev = devm_input_allocate_device(&pdev->dev);
> 143 if (!input_dev) {
> 144 dev_err(&pdev->dev, "failed to allocate the input device\n");
> 145 return -ENOMEM;
> 146 }
> 147
> 148 input_dev->name = pdev->name;
> 149 input_dev->phys = "keyscan-keys/input0";
> 150 input_dev->dev.parent = &pdev->dev;
> 151 input_dev->open = keyscan_open;
> 152 input_dev->close = keyscan_close;
> 153
> 154 input_dev->id.bustype = BUS_HOST;
> 155
> --> 156 error = keypad_matrix_key_parse_dt(keypad_data);
> ^^^^^^^^^^^
I agree with you this would be a problem
to clarify the NULL derefence would occur here within keypad_matrix_key_parse_dt

struct device *dev = keypad_data->input_dev->dev.parent;

> This assumes we have set "keypad_data->input_dev = input_dev;" but we
> don't do that until...
>
> 157 if (error)
> 158 return error;
> 159
> 160 error = matrix_keypad_build_keymap(NULL, NULL,
> 161 keypad_data->n_rows,
> 162 keypad_data->n_cols,
> 163 NULL, input_dev);
> 164 if (error) {
> 165 dev_err(&pdev->dev, "failed to build keymap\n");
> 166 return error;
> 167 }
> 168
> 169 input_set_drvdata(input_dev, keypad_data);
> 170
> 171 keypad_data->input_dev = input_dev;
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> this line here. This driver has never worked and it was included almost
> five years ago. Is it worth fixing?
>
> 172
> 173 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> 174 keypad_data->base = devm_ioremap_resource(&pdev->dev, res);
> 175 if (IS_ERR(keypad_data->base))
> 176 return PTR_ERR(keypad_data->base);
> 177
>
> regards,
> dan carpenter
>

Here is the interesting thing, I was looking on patchwork, and several
of the patches including what appears to be the latest actually set
"keypad_data->input_dev = input_dev" before calling
"keypad_matrix_key_parse_dt"

From v4 on patchwork
+ if (IS_ERR(keypad_data->clk)) {
+ dev_err(&pdev->dev, "cannot get clock");
+ return PTR_ERR(keypad_data->clk);
+ }
+
+ keypad_data->input_dev = input_dev;
+
+ input_dev->name = pdev->name;
+ input_dev->phys = "keyscan-keys/input0";
+ input_dev->dev.parent = &pdev->dev;
+ input_dev->open = keyscan_open;
+ input_dev->close = keyscan_close;
+
+ input_dev->id.bustype = BUS_HOST;
+
+ error = keypad_matrix_key_parse_dt(keypad_data);

According to patchwork, these aren't listed as accepted, so I'm not
sure where the exact accepted patch came from. Looking at the commit
log, it looks like the issue you showed above was made in the original
commit 062589b1399176a9c14bc68e16169f40439d658c so I'm not quite sure
what is going on here. Maybe the maintainer can chime in with the
original patch/mailing list discussion on this. For reference, I've
added the patchwork links below
https://patchwork.kernel.org/patch/3854341/
https://patchwork.kernel.org/patch/3968891/
https://patchwork.kernel.org/patch/3969991/

Thanks,
Ken Sloat

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