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

[Can Guo]

On 2021-01-12 14:35, Stanley Chu wrote:

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 <c...@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?

Yes, you are right. I think it is possible. platform_set_drvdata()
is called in ufshcd_pltfrm_init(). Say suspend happens before
platform_set_drvdata() is called, but resume comes back after
platform_set_drvdata() is called. What do you think?

Thanks,
Can Guo.

Thanks a lot.
Stanley Chu

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