Re: [PATCH 3/4] zfcp: trace return values of sysfs unit add store

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Uninitialized kernel stack memory (`fcp_lun`) is written to a debug trace buffer when `kstrtoull` parsing fails, causing an information leak to userspace.
--

--- Patch [3]: [PATCH 3/4] zfcp: trace return values of sysfs unit add store ---
commit 2f001159c00d2d39b83745c171b53d3cb2468df3
Author: Chinmaya Kajagar <chinmayk@linux.ibm.com>

zfcp: trace return values of sysfs unit add store

This commit adds tracing for unit_add sysfs attribute failures to help
debug issues where the kernel cannot add a LUN. It adds a new trace record
ZFCP_DBF_HBA_UAS and updates zfcp_sysfs_unit_add_store() to log these events.

> diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c
> index 42423549e511d..729c9664a48f8 100644
> --- a/drivers/s390/scsi/zfcp_sysfs.c
> +++ b/drivers/s390/scsi/zfcp_sysfs.c
[ ... ]
> @@ -442,17 +442,24 @@ static ssize_t zfcp_sysfs_unit_add_store(struct device *dev,
>  					 const char *buf, size_t count)
>  {
>  	struct zfcp_port *port = container_of(dev, struct zfcp_port, dev);
> +	struct zfcp_adapter *adapter = port->adapter;
>  	u64 fcp_lun;
> -	int retval;
> +	int retval = -EINVAL;
>  
> -	if (kstrtoull(buf, 0, (unsigned long long *) &fcp_lun))
> -		return -EINVAL;
> +	if (kstrtoull(buf, 0, (unsigned long long *)&fcp_lun)) {
> +		zfcp_dbf_hba_uas("syuast1", 3, adapter, port->wwpn,
> +				 fcp_lun, retval);

[Severity: Medium]
Does this code leak uninitialized kernel stack memory into the trace buffer?

If kstrtoull() fails to parse the input, it returns an error and may not
write to fcp_lun. The uninitialized fcp_lun variable is then immediately
passed to zfcp_dbf_hba_uas(), which records it in the trace buffer that
can be read from userspace.

> +		return retval;
> +	}
>  
>  	flush_work(&port->rport_work);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260724053934.2781087-1-niharp@linux.ibm.com?part=3