[lvc-project] [PATCH] mmc: dw_mmc: Fix potential null pointer risk

[Мишин Александр Борисович]

At the same time there are few checks such as "if (host->slot)" in dw_mci_runtime_resume() and commit 4a835afd808a3dbbac44bb399a902b822dc7445c message contains: "we previously assumed 'host->slot' could be null, null pointer judgment should be added" and replaces "if (host->slot->mmc->pm_flags & MMC_PM_KEEP_POWER)" with "if (host->slot && host->slot->mmc->pm_flags & MMC_PM_KEEP_POWER)"
So where is the truth?

Kind regards

Aleksandr


________________________________
От: Ulf Hansson <ulf.hansson at linaro.org>
Отправлено: 7 марта 2024 г. 13:57:16
Кому: Мишин Александр Борисович
Копия: Jaehoon Chung; Wen Zhiwei; linux-mmc at vger.kernel.org; linux-kernel at vger.kernel.org; lvc-project at linuxtesting.org
Тема: Re: [PATCH] mmc: dw_mmc: Fix potential null pointer risk

On Thu, 7 Mar 2024 at 09:53, Aleksandr Mishin <amishin at t-argos.ru> wrote:
>
> In dw_mci_runtime_resume() 'host->slot' could be null, but check is not cover all corresponding code.
> Fix this bug by changing check place.

In fact host->slot can never be NULL in dw_mci_runtime_resume() or in
dw_mci_runtime_suspend().

A better fix would thus be to remove the redundant checks.

Kind regards
Uffe

>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: 4a835afd808a (mmc: dw_mmc: Fix potential null pointer risk)
> Signed-off-by: Aleksandr Mishin <amishin at t-argos.ru>
> ---
>  drivers/mmc/host/dw_mmc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 829af2c98a44..a4f124452abc 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -3570,8 +3570,10 @@ int dw_mci_runtime_resume(struct device *dev)
>                    DW_MCI_ERROR_FLAGS);
>         mci_writel(host, CTRL, SDMMC_CTRL_INT_ENABLE);
>
> +       if (!host->slot)
> +               goto err;
>
> -       if (host->slot && host->slot->mmc->pm_flags & MMC_PM_KEEP_POWER)
> +       if (host->slot->mmc->pm_flags & MMC_PM_KEEP_POWER)
>                 dw_mci_set_ios(host->slot->mmc, &host->slot->mmc->ios);
>
>         /* Force setup bus to guarantee available clock output */
> --
> 2.30.2
>
>
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