linux-kernel - [PATCH V4] scsi: lpfc: Fix a possible null pointer dereference

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Message-Id: <20240621082545.449170-1-qq810974084@gmail.com>
Date: Fri, 21 Jun 2024 16:25:45 +0800
From: Huai-Yuan Liu <qq810974084@...il.com>
To: james.smart@...adcom.com,
	dick.kennedy@...adcom.com,
	James.Bottomley@...senPartnership.com,
	martin.petersen@...cle.com
Cc: linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	baijiaju1990@...il.com,
	Huai-Yuan Liu <qq810974084@...il.com>
Subject: [PATCH V4] scsi: lpfc: Fix a possible null pointer dereference

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,
use scnprintf to notify the user and return len.

Fixes: 479b0917e447 ("scsi: lpfc: Create a sysfs entry called lpfc_xcvr_data for transceiver info")
Signed-off-by: Huai-Yuan Liu <qq810974084@...il.com>
---
V2:
* In patch V2, we have removed the unnecessary 'out of memory' message.
  Thank Bart Van Assche for helpful advice.
V3:
* In patch V3, we return len directly instead of goto out_free_rdp.
  Thanks to Justin Tee for his suuestion.
V4:
* In patch V4, we log something before return len, which would result in a
silent when len is 0.
  Thanks to Justin Tee again for additional explanation.
---
 drivers/scsi/lpfc/lpfc_attr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
index a46c73e8d7c4..0a9d6978cb0c 100644
--- a/drivers/scsi/lpfc/lpfc_attr.c
+++ b/drivers/scsi/lpfc/lpfc_attr.c
@@ -1907,6 +1907,11 @@ 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) {
+		len = scnprintf(buf, PAGE_SIZE - len,
+				"SPF info NA: alloc failure\n");
+		return len;
+	}
 
 	rc = lpfc_get_sfp_info_wait(phba, rdp_context);
 	if (rc) {
-- 
2.34.1