[PATCH V2 RESEND] scsi: lpfc: Fix a possible null pointer dereference

[PATCH V2 RESEND] scsi: lpfc: Fix a possible null pointer dereference

[Huai-Yuan Liu]

In function lpfc_xcvr_data_show, the memory allocation with kmalloc might
fail, thereby making rdp_context a null pointer. In the following context 
and functions that use this pointer, there are dereferencing operations,
leading to null pointer dereference.

To fix this issue, a null pointer check should be added. If it is null, 
just jump to 'out_free_rdp'.

Fixes: 479b0917e447 ("scsi: lpfc: Create a sysfs entry called lpfc_xcvr_data for transceiver info")
Signed-off-by: Huai-Yuan Liu <qq810974084@gmail.com>
---
V2:
* In patch V2, we have removed the unnecessary 'out of memory' message.
  Thank Bart Van Assche for helpful advice.
---
 drivers/scsi/lpfc/lpfc_attr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
index b1c9107d3408..94d968a255ff 100644
--- a/drivers/scsi/lpfc/lpfc_attr.c
+++ b/drivers/scsi/lpfc/lpfc_attr.c
@@ -1904,6 +1904,8 @@ lpfc_xcvr_data_show(struct device *dev, struct device_attribute *attr,
 
 	/* Get transceiver information */
 	rdp_context = kmalloc(sizeof(*rdp_context), GFP_KERNEL);
+	if (!rdp_context)
+		goto out_free_rdp;
 
 	rc = lpfc_get_sfp_info_wait(phba, rdp_context);
 	if (rc) {
-- 
2.34.1

Re: [PATCH V2 RESEND] scsi: lpfc: Fix a possible null pointer dereference

[Justin Tee]

Hi Huai-Yuan,

> diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
> index b1c9107d3408..94d968a255ff 100644
> --- a/drivers/scsi/lpfc/lpfc_attr.c
> +++ b/drivers/scsi/lpfc/lpfc_attr.c
> @@ -1904,6 +1904,8 @@ lpfc_xcvr_data_show(struct device *dev, struct device_attribute *attr,
>
>         /* Get transceiver information */
>         rdp_context = kmalloc(sizeof(*rdp_context), GFP_KERNEL);
> +       if (!rdp_context)
> +               goto out_free_rdp;

Understood that kfree(NULL) essentially translates to no-op, but I'd
prefer that we return len here instead of goto out_free_rdp because
there really is nothing to free if kmalloc failed.

Thanks,
Justin