linux-kernel - [PATCH 6.1] HID: mcp2221: Set driver data before I2C adapter add

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Message-ID: <20250716195316.176786-1-sumanth.gavini@yahoo.com>
Date: Wed, 16 Jul 2025 14:53:13 -0500
From: Sumanth Gavini <sumanth.gavini@...oo.com>
To: skhan@...uxfoundation.org,
	david.hunter.linux@...il.com,
	gupt21@...il.com,
	jikos@...nel.org,
	benjamin.tissoires@...hat.com
Cc: Sumanth Gavini <sumanth.gavini@...oo.com>,
	stable@...r.kernel.org,
	linux-i2c@...r.kernel.org,
	linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Hamish Martin <hamish.martin@...iedtelesis.co.nz>,
	Jiri Kosina <jkosina@...e.cz>
Subject: [PATCH 6.1] HID: mcp2221: Set driver data before I2C adapter add

The process of adding an I2C adapter can invoke I2C accesses on that new
adapter (see i2c_detect()).

Ensure we have set the adapter's driver data to avoid null pointer
dereferences in the xfer functions during the adapter add.

This has been noted in the past and the same fix proposed but not
completed. See:
https://lore.kernel.org/lkml/ef597e73-ed71-168e-52af-0d19b03734ac@vigem.de/

Signed-off-by: Hamish Martin <hamish.martin@...iedtelesis.co.nz>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Sumanth Gavini <sumanth.gavini@...oo.com>
---
 drivers/hid/hid-mcp2221.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
index de52e9f7bb8c..9973545c1c4b 100644
--- a/drivers/hid/hid-mcp2221.c
+++ b/drivers/hid/hid-mcp2221.c
@@ -873,12 +873,12 @@ static int mcp2221_probe(struct hid_device *hdev,
 			"MCP2221 usb-i2c bridge on hidraw%d",
 			((struct hidraw *)hdev->hidraw)->minor);
 
+	i2c_set_adapdata(&mcp->adapter, mcp);
 	ret = i2c_add_adapter(&mcp->adapter);
 	if (ret) {
 		hid_err(hdev, "can't add usb-i2c adapter: %d\n", ret);
 		goto err_i2c;
 	}
-	i2c_set_adapdata(&mcp->adapter, mcp);
 
 	/* Setup GPIO chip */
 	mcp->gc = devm_kzalloc(&hdev->dev, sizeof(*mcp->gc), GFP_KERNEL);
-- 
2.43.0