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

[Can Guo]

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 <c...@codeaurora.org>
---
 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!hba there, they are outdated.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.