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Message-ID: <0f053152-a70d-45b9-9924-4c0f728d0b97@kernel.org> Date: Sat, 18 Nov 2023 12:05:07 +0200 From: Roger Quadros <rogerq@...nel.org> To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de> Cc: Siddharth Vadapalli <s-vadapalli@...com>, Ravi Gunasekaran <r-gunasekaran@...com>, Simon Horman <horms@...nel.org>, Yunsheng Lin <linyunsheng@...wei.com>, Stanislav Fomichev <sdf@...gle.com>, Marek Majtyka <alardam@...il.com>, Rob Herring <robh@...nel.org>, Mugunthan V N <mugunthanvnm@...com>, linux-omap@...r.kernel.org, netdev@...r.kernel.org, kernel@...gutronix.de Subject: Re: [PATCH 2/7] net: ethernet: ti: cpsw: Don't error out in .remove() On 18/11/2023 12:00, Roger Quadros wrote: > > > 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@...gutronix.de> >> --- >> 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? cpdma_chan_destroy() does a cpdma_chan_stop() which does register accesses so I suppose it cannot be called in the error path. which leaves only the cpdma_desc_pool_destroy() call. > >> + } >> + >> cpsw_remove_dt(pdev); >> pm_runtime_put_sync(&pdev->dev); >> pm_runtime_disable(&pdev->dev); > -- cheers, -roger
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