linux-kernel - [PATCH V2 6.1] HID: mcp2221: Set driver data before I2C adapter add

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Message-ID: <20250717000151.183803-1-sumanth.gavini@yahoo.com>
Date: Wed, 16 Jul 2025 19:01:50 -0500
From: Sumanth Gavini <sumanth.gavini@...oo.com>
To: lkp@...el.com,
	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,
	oe-kbuild-all@...ts.linux.dev,
	Hamish Martin <hamish.martin@...iedtelesis.co.nz>,
	Jiri Kosina <jkosina@...e.cz>
Subject: [PATCH V2 6.1] HID: mcp2221: Set driver data before I2C adapter add

commit f1228f4d4254dfad837f1a1e4c69930417798047 upstream.

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>
---
changes in v2:
- No code changes
- Link to v1:https://lore.kernel.org/stable/20250716195316.176786-1-sumanth.gavini@yahoo.com/
- Updated the upstream commit ID in the log
---
 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