Re: [PATCH 1/2] scsi: ufs: Fix a possible NULL pointer issue

Stanley Chu
2021-01-12T06:36:36Z

Hi Can,

On Sat, 2021-01-02 at 05:59 -0800, Can Guo wrote:
> During system resume/suspend, hba could be NULL. In this case, do not touch
> eh_sem.
>
> Fixes: 88a92d6ae4fe ("scsi: ufs: Serialize eh_work with system PM events and async scan")
>
> Signed-off-by: Can Guo <cang@codeaurora.org>
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index e221add..9829c8d 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -94,6 +94,8 @@
> 16, 4, buf, __len, false); \
> } while (0)
>
> +static bool early_suspend;
> +
> int ufshcd_dump_regs(struct ufs_hba *hba, size_t offset, size_t len,
> const char *prefix)
> {
> @@ -8896,8 +8898,14 @@ int ufshcd_system_suspend(struct ufs_hba *hba)
> int ret = 0;
> ktime_t start = ktime_get();
>
> + if (!hba) {
> + early_suspend = true;
> + return 0;
> + }
> +
> down(&hba->eh_sem);
> - if (!hba || !hba->is_powered)
> +
> + if (!hba->is_powered)
> return 0;
>
> if ((ufs_get_pm_lvl_to_dev_pwr_mode(hba->spm_lvl) ==
> @@ -8945,9 +8953,12 @@ int ufshcd_system_resume(struct ufs_hba *hba)
> int ret = 0;
> ktime_t start = ktime_get();
>
> - if (!hba) {
> - up(&hba->eh_sem);
> + if (!hba)
> return -EINVAL;
> +
> + if (unlikely(early_suspend)) {
> + early_suspend = false;
> + down(&hba->eh_sem);
> }

I guess early_suspend here is to handle the case that hba is null during
ufshcd_system_suspend() but !null during ufshcd_system_resume(). If yes,
would it be possible? If no, may I know what is the purpose?

Thanks a lot.
Stanley Chu

>
> if (!hba->is_powered || pm_runtime_suspended(hba->dev))