Hi!
2023-10-19 at 09:35, Herve Codina wrote:
> i2c-mux-gpmux uses the pair of_find_i2c_adapter_by_node() /
> i2c_put_adapter(). These pair alone is not correct to properly lock the
> I2C parent adapter.
>
> Indeed, i2c_put_adapter() decrements the module refcount while
> of_find_i2c_adapter_by_node() does not increment it. This leads to an
> overflow over zero of the parent adapter user counter.
Perhaps "... underflow of the parent module refcount."?
>
> Use the dedicated function, of_get_i2c_adapter_by_node(), to handle
> correctly the module refcount.
>
> Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
Good find, and sorry about that!
Fixes: ac8498f0ce53 ("i2c: i2c-mux-gpmux: new driver")
Acked-by: Peter Rosin <peda@xxxxxxxxxx>
Cheers,
Peter
> ---
> drivers/i2c/muxes/i2c-mux-gpmux.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/muxes/i2c-mux-gpmux.c b/drivers/i2c/muxes/i2c-mux-gpmux.c
> index baccf4bfaf02..8305661e1253 100644
> --- a/drivers/i2c/muxes/i2c-mux-gpmux.c
> +++ b/drivers/i2c/muxes/i2c-mux-gpmux.c
> @@ -52,7 +52,7 @@ static struct i2c_adapter *mux_parent_adapter(struct device *dev)
> dev_err(dev, "Cannot parse i2c-parent\n");
> return ERR_PTR(-ENODEV);
> }
> - parent = of_find_i2c_adapter_by_node(parent_np);
> + parent = of_get_i2c_adapter_by_node(parent_np);
> of_node_put(parent_np);
> if (!parent)
> return ERR_PTR(-EPROBE_DEFER);
