Subject: [PATCH net-next] net: arcnet: com20020-pci: fix support for 2.5Mbit cards

From: Ethan Nelson-Moore <[email-masked]>
Date: Wed, 4 Feb 2026 22:51:12 -0800

Commit 8c14f9c70327 ("ARCNET: add com20020 PCI IDs with metadata")
converted the com20020-pci driver to use a card info structure instead
of a single flag mask in driver_data. However, it failed to take into
account that in the original code, driver_data of 0 indicates a card
with no special flags, not a card that should not have any card info
structure. This introduced a null pointer dereference when cards with
no flags were probed.

Commit bd6f1fd5d33d ("net: arcnet: com20020: Fix null-ptr-deref in
com20020pci_probe()") then papered over this issue by rejecting cards
with no driver_data instead of resolving the problem at its source.

Revert the incorrect fix and fix the original issue by introducing a
new card info structure for 2.5Mbit cards that does not set any flags.

Fixes: 8c14f9c70327 ("ARCNET: add com20020 PCI IDs with metadata")
Fixes: bd6f1fd5d33d ("net: arcnet: com20020: Fix null-ptr-deref in com20020pci_probe()")
Cc: [email-masked]
Signed-off-by: Ethan Nelson-Moore <[email-masked]>
---
 drivers/net/arcnet/com20020-pci.c | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/net/arcnet/com20020-pci.c b/drivers/net/arcnet/com20020-pci.c
index 0472bcdff130..4847f40a2095 100644
--- a/drivers/net/arcnet/com20020-pci.c
+++ b/drivers/net/arcnet/com20020-pci.c
@@ -139,9 +139,6 @@ static int com20020pci_probe(struct pci_dev *pdev,
 		return -ENOMEM;
 
 	ci = (struct com20020_pci_card_info *)id->driver_data;
-	if (!ci)
-		return -EINVAL;
-
 	priv->ci = ci;
 	mm = &ci->misc_map;
 
@@ -347,6 +344,18 @@ static struct com20020_pci_card_info card_info_5mbit = {
 	.flags = ARC_IS_5MBIT,
 };
 
+static struct com20020_pci_card_info card_info_2p5mbit = {
+	.name = "ARC-PCI",
+	.devcount = 1,
+	.chan_map_tbl = {
+		{
+			.bar = 2,
+			.offset = 0x00,
+			.size = 0x08,
+		},
+	},
+};
+
 static struct com20020_pci_card_info card_info_sohard = {
 	.name = "SOHARD SH ARC-PCI",
 	.devcount = 1,
@@ -448,49 +457,49 @@ static const struct pci_device_id com20020pci_id_table[] = {
 		0x1571, 0xa001,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0,
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa002,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0,
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa003,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa004,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0,
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa005,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa006,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa007,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa008,
 		PCI_ANY_ID, PCI_ANY_ID,
 		0, 0,
-		0
+		(kernel_ulong_t)&card_info_2p5mbit
 	},
 	{
 		0x1571, 0xa009,
-- 
2.43.0