On 17/11/2023 11:16, Uwe Kleine-König wrote:
> Returning early from .remove() with an error code still results in the
> driver unbinding the device. So the driver core ignores the returned error
> code and the resources that were not freed are never catched up. In
> combination with devm this also often results in use-after-free bugs.
>
> If runtime resume fails, it's still important to free all resources, so
> don't return with an error code, but emit an error message and continue
> freeing acquired stuff.
>
> This prepares changing cpsw_remove() to return void.
>
> Fixes: 8a0b6dc958fd ("drivers: net: cpsw: fix wrong regs access in cpsw_remove")
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
> ---
> drivers/net/ethernet/ti/cpsw.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
> index ca4d4548f85e..db5a2ba8a6d4 100644
> --- a/drivers/net/ethernet/ti/cpsw.c
> +++ b/drivers/net/ethernet/ti/cpsw.c
> @@ -1727,16 +1727,24 @@ static int cpsw_remove(struct platform_device *pdev)
> struct cpsw_common *cpsw = platform_get_drvdata(pdev);
> int i, ret;
>
> - ret = pm_runtime_resume_and_get(&pdev->dev);
> + ret = pm_runtime_get_sync(&pdev->dev);
> if (ret < 0)
> - return ret;
> + /* There is no need to do something about that. The important
> + * thing is to not exit early, but do all cleanup that doesn't
> + * require register access.
> + */
> + dev_err(&pdev->dev, "runtime resume failed (%pe)\n",
> + ERR_PTR(ret));
>
> for (i = 0; i < cpsw->data.slaves; i++)
> if (cpsw->slaves[i].ndev)
> unregister_netdev(cpsw->slaves[i].ndev);
>
> - cpts_release(cpsw->cpts);
> - cpdma_ctlr_destroy(cpsw->dma);
> + if (ret >= 0) {
> + cpts_release(cpsw->cpts);
cpts_release() only does clk_unprepare().
Why not do that in the error path as well?
> + cpdma_ctlr_destroy(cpsw->dma);
cpdma_ctrl_destroy() not only stops the DMA controller
but also frees up the channel and calls dma_free_coherent?
We still want to free up the channel and dma_free_coherent in the
error path?
> + }
> +
> cpsw_remove_dt(pdev);
> pm_runtime_put_sync(&pdev->dev);
> pm_runtime_disable(&pdev->dev);
--
cheers,
-roger
