Re: [PATCH v2 5/5] scsi: ufs: core: Clear stale UIC result byte before peer DME retries

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] ufs: race in ufshcd_dispatch_uic_cmd() between retry and late interrupt
--

commit 2dc892f166dff54aa2e190ad9b52806532df339b
Author: Stanley Jhu <stanleyjhu@google.com>

scsi: ufs: core: Clear stale UIC result byte before peer DME retries

This commit clears the stale UIC result byte and restores argument3 when an
attempt fails before peer DME retries. This prevents a transient failure from
becoming a hard failure after retries due to uncleared error codes.

> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index bcc2512bf34b8..7532fd916bfd9 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -4400,9 +4400,12 @@ int ufshcd_dme_set_attr(struct ufs_hba *hba, u32 attr_sel,
>  	do {
>  		/* for peer attributes we retry upon failure */
>  		ret = ufshcd_send_uic_cmd(hba, &uic_cmd);
> -		if (ret)
> +		if (ret) {
>  			dev_dbg(hba->dev, "%s: attr-id 0x%x val 0x%x error code %d\n",
>  				set, UIC_GET_ATTR_ID(attr_sel), mib_val, ret);
> +			uic_cmd.argument2 &= ~MASK_UIC_COMMAND_RESULT;
> +			uic_cmd.argument3 = mib_val;
> +		}
>  	} while (ret && peer && --retries);

[Severity: High]
Can a retried UIC command be prematurely completed by a late interrupt from a
previous timed-out command?

If a call to ufshcd_send_uic_cmd() times out, the retry loop immediately
invokes it again. In ufshcd_dispatch_uic_cmd(), the new command is assigned
to hba->active_uic_cmd without holding the host_lock:

drivers/ufs/core/ufshcd.c:ufshcd_dispatch_uic_cmd() {
    ...
    hba->active_uic_cmd = uic_cmd;
    ...
}

If a late interrupt from the previously timed-out command fires right after
this assignment, the ISR will read the new command under host_lock and
complete it prematurely:

drivers/ufs/core/ufshcd.c:ufshcd_uic_cmd_compl() {
    ...
    guard(spinlock_irqsave)(&hba->host->host_lock);
    cmd = hba->active_uic_cmd;
    if (!cmd) {
    ...
}

This could lead to invalid configuration and potential controller
desynchronization, since the new command is completed using the old command's
result.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261015001855.3450573-1-stanleyjhu@google.com?part=5