netdev - [PATCH net] ibmvnic: Use kernel helpers for hex dumps

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Message-ID: <20250320212951.11142-1-nnac123@linux.ibm.com>
Date: Thu, 20 Mar 2025 16:29:51 -0500
From: Nick Child <nnac123@...ux.ibm.com>
To: netdev@...r.kernel.org
Cc: davemarq@...ux.ibm.com, haren@...ux.ibm.com, ricklind@...ibm.com,
        Nick Child <nnac123@...ux.ibm.com>
Subject: [PATCH net] ibmvnic: Use kernel helpers for hex dumps

Previously, when the driver was printing hex dumps, the buffer was cast
to an 8 byte long and printed using string formatters. If the buffer
size was not a multiple of 8 then a read buffer overflow was possible.

Therefore, create a new ibmvnic function that loops over a buffer and
calls hex_dump_to_buffer instead.

This patch address KASAN reports like the one below:
  ibmvnic 30000003 env3: Login Buffer:
  ibmvnic 30000003 env3: 01000000af000000
  <...>
  ibmvnic 30000003 env3: 2e6d62692e736261
  ibmvnic 30000003 env3: 65050003006d6f63
  ==================================================================
  BUG: KASAN: slab-out-of-bounds in ibmvnic_login+0xacc/0xffc [ibmvnic]
  Read of size 8 at addr c0000001331a9aa8 by task ip/17681
  <...>
  Allocated by task 17681:
  <...>
  ibmvnic_login+0x2f0/0xffc [ibmvnic]
  ibmvnic_open+0x148/0x308 [ibmvnic]
  __dev_open+0x1ac/0x304
  <...>
  The buggy address is located 168 bytes inside of
                allocated 175-byte region [c0000001331a9a00, c0000001331a9aaf)
  <...>
  =================================================================
  ibmvnic 30000003 env3: 000000000033766e

Fixes: 032c5e82847a ("Driver for IBM System i/p VNIC protocol")
Signed-off-by: Nick Child <nnac123@...ux.ibm.com>
Reviewed-by: Dave Marquardt <davemarq@...ux.ibm.com>
---
This patch obsoletes my work to define a for_each macro in printk.h [1]. It was
determined the pitfalls outweighed the benefits of the code cleanup.

Side question, is net the correct mailing list even if the bug being addressed
was introduced long before the current release? Or is net-next more appropriate?
Does bug severity play any part in this or does anything with a Fixes tag go to
net? netdev-FAQ implies all fixes go into net but previous mailing list entries
seem to vary. Thanks

[1] https://lore.kernel.org/lkml/20250219211102.225324-1-nnac123@linux.ibm.com/

 drivers/net/ethernet/ibm/ibmvnic.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 0676fc547b6f..480606d1245e 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -4829,6 +4829,18 @@ static void vnic_add_client_data(struct ibmvnic_adapter *adapter,
 	strscpy(vlcd->name, adapter->netdev->name, len);
 }
 
+static void ibmvnic_print_hex_dump(struct net_device *dev, void *buf,
+				   size_t len)
+{
+	unsigned char hex_str[16 * 3];
+
+	for (size_t i = 0; i < len; i += 16) {
+		hex_dump_to_buffer((unsigned char *)buf + i, len - i, 16, 8,
+				   hex_str, sizeof(hex_str), false);
+		netdev_dbg(dev, "%s\n", hex_str);
+	}
+}
+
 static int send_login(struct ibmvnic_adapter *adapter)
 {
 	struct ibmvnic_login_rsp_buffer *login_rsp_buffer;
@@ -4939,10 +4951,8 @@ static int send_login(struct ibmvnic_adapter *adapter)
 	vnic_add_client_data(adapter, vlcd);
 
 	netdev_dbg(adapter->netdev, "Login Buffer:\n");
-	for (i = 0; i < (adapter->login_buf_sz - 1) / 8 + 1; i++) {
-		netdev_dbg(adapter->netdev, "%016lx\n",
-			   ((unsigned long *)(adapter->login_buf))[i]);
-	}
+	ibmvnic_print_hex_dump(adapter->netdev, adapter->login_buf,
+			       adapter->login_buf_sz);
 
 	memset(&crq, 0, sizeof(crq));
 	crq.login.first = IBMVNIC_CRQ_CMD;
@@ -5319,15 +5329,13 @@ static void handle_query_ip_offload_rsp(struct ibmvnic_adapter *adapter)
 {
 	struct device *dev = &adapter->vdev->dev;
 	struct ibmvnic_query_ip_offload_buffer *buf = &adapter->ip_offload_buf;
-	int i;
 
 	dma_unmap_single(dev, adapter->ip_offload_tok,
 			 sizeof(adapter->ip_offload_buf), DMA_FROM_DEVICE);
 
 	netdev_dbg(adapter->netdev, "Query IP Offload Buffer:\n");
-	for (i = 0; i < (sizeof(adapter->ip_offload_buf) - 1) / 8 + 1; i++)
-		netdev_dbg(adapter->netdev, "%016lx\n",
-			   ((unsigned long *)(buf))[i]);
+	ibmvnic_print_hex_dump(adapter->netdev, buf,
+			       sizeof(adapter->ip_offload_buf));
 
 	netdev_dbg(adapter->netdev, "ipv4_chksum = %d\n", buf->ipv4_chksum);
 	netdev_dbg(adapter->netdev, "ipv6_chksum = %d\n", buf->ipv6_chksum);
@@ -5558,10 +5566,8 @@ static int handle_login_rsp(union ibmvnic_crq *login_rsp_crq,
 	netdev->mtu = adapter->req_mtu - ETH_HLEN;
 
 	netdev_dbg(adapter->netdev, "Login Response Buffer:\n");
-	for (i = 0; i < (adapter->login_rsp_buf_sz - 1) / 8 + 1; i++) {
-		netdev_dbg(adapter->netdev, "%016lx\n",
-			   ((unsigned long *)(adapter->login_rsp_buf))[i]);
-	}
+	ibmvnic_print_hex_dump(netdev, adapter->login_rsp_buf,
+			       adapter->login_rsp_buf_sz);
 
 	/* Sanity checks */
 	if (login->num_txcomp_subcrqs != login_rsp->num_txsubm_subcrqs ||
-- 
2.48.1