Hi Teng Qi,
On Tue, Apr 25, 2023 at 07:49:51AM +0000, starmiku1207184332@xxxxxxxxx wrote:
> From: Teng Qi <starmiku1207184332@xxxxxxxxx>
>
> input_alloc_absinfo() may cause the kernel to sleep by calling kcalloc() with
> the GFP_KERNEL flag. It may be called by input_event() holding spinlock through
> the following call path:
>
> input_event(), 433
> input_handle_event(), 399
> input_get_disposition(), 294
> input_handle_abs_event(), 232
> input_abs_set_val(), Clang suggests it calls input_alloc_absinfo()
> unconditionally
> input_alloc_absinfo(), 483
> kcalloc(..., GFP_KERNEL)
>
> This call path can potentially trigger a sleep-in-atomic bug. To prevent this
> potential bug, we modify input_alloc_absinfo() to use the GFP_ATOMIC flag
> instead of the GFP_KERNEL flag.
This can not happen in practice, and changing the allocation type to
GFP_ATOMIC hurts the other code. We can avoid the issue by not using the
helper and have input core access the slot info directly. I CCed you on
a patch doing so.
> The possible bug is detected by a static code analysis tool.
>
> Signed-off-by: Teng Qi <starmiku1207184332@xxxxxxxxx>
> ---
> drivers/input/input.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/input/input.c b/drivers/input/input.c
> index 37e876d45eb9..eefc4c85a693 100644
> --- a/drivers/input/input.c
> +++ b/drivers/input/input.c
> @@ -480,7 +480,7 @@ void input_alloc_absinfo(struct input_dev *dev)
> if (dev->absinfo)
> return;
>
> - dev->absinfo = kcalloc(ABS_CNT, sizeof(*dev->absinfo), GFP_KERNEL);
> + dev->absinfo = kcalloc(ABS_CNT, sizeof(*dev->absinfo), GFP_ATOMIC);
> if (!dev->absinfo) {
> dev_err(dev->dev.parent ?: &dev->dev,
> "%s: unable to allocate memory\n", __func__);
> --
> 2.25.1
>
Thanks.
--
Dmitry
