Re: [PATCH v2 1/2] scsi: ufs: Fix a possible NULL pointer issue

From: Can Guo
Date: Sat Jan 02 2021 - 07:46:48 EST


On 2021-01-02 00:05, Bart Van Assche wrote:
On 12/31/20 9:44 PM, 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@xxxxxxxxxxxxxx>
---
drivers/scsi/ufs/ufshcd.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index e221add..34e2541 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -8896,8 +8896,11 @@ int ufshcd_system_suspend(struct ufs_hba *hba)
int ret = 0;
ktime_t start = ktime_get();

+ if (!hba)
+ 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) ==
@@ -8945,10 +8948,8 @@ 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 (!hba->is_powered || pm_runtime_suspended(hba->dev))
/*

Hi Can,

How can ufshcd_system_suspend() or ufshcd_system_resume() be called with a
NULL argument? In ufshcd_pci_probe() I see that pci_set_drvdata() is called
before pm_runtime_allow(). ufshcd_pci_remove() calls pm_runtime_forbid().

Thanks,

Bart.

Hi Bart,

You are right about ufshcd_RUNTIME_suspend/resume() - platform_set_drvdata()
is called before pm_runtime_enable(), so runtime suspend/resume cannot happen
before pm_runtime_enable() is called. We can remove the sanity checks of
!hba there, they are outdated.

But for ufshcd_SYSTEM_suspend/resume() callbacks (not runtime ones), my
understanding is that system suspend/resume may happen after probe (vendor
driver probe calls ufshcd_pltfrm_init()) starts but before platform_set_drvdata()
is called, in this case hba is NULL.

int ufshcd_pltfrm_init(struct platform_device *pdev,
const struct ufs_hba_variant_ops *vops)
{
...
platform_set_drvdata(pdev, hba);

pm_runtime_set_active(&pdev->dev);
pm_runtime_enable(&pdev->dev);
}

Thanks,

Can Guo.