Re: [PATCH 3/3] 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 stack variable `fcp_lun` is logged to the debugfs trace buffer when `kstrtoull()` fails, leaking kernel stack memory.
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commit 907efa1a4b46ed7f2ac643c1a75f4e115a834154
Author: Chinmaya Kajagar <chinmayk@linux.ibm.com>

zfcp: trace return values of sysfs unit add store

This commit adds tracing for zfcp sysfs unit add failures to help debug
cases where the kernel cannot add a LUN. It records the wwpn, fcp lun id,
return value, and associated hba of the device.

> diff --git a/drivers/s390/scsi/zfcp_sysfs.c b/drivers/s390/scsi/zfcp_sysfs.c
> --- 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]
Is there a risk of leaking kernel stack memory into the trace buffer here?

If kstrtoull() fails to parse the input string, it returns an error and
leaves the stack-allocated fcp_lun unmodified.

Since fcp_lun is uninitialized, this trace call passes 8 bytes of
uninitialized stack memory to zfcp_dbf_hba_uas(), which might expose it
via the DBF trace ring buffer and result in misleading garbage LUN values
in the log.

> +		return retval;
> +	}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260611050550.796772-1-niharp@linux.ibm.com?part=3