linux-kernel - [PATCH v2] HID: mcp-2221: prevent UAF in delayed work

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Date:   Thu, 16 Feb 2023 11:22:58 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Rishi Gupta <gupt21@...il.com>, Jiri Kosina <jikos@...nel.org>,
        Pietro Borrello <borrello@...g.uniroma1.it>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Subject: [PATCH v2] HID: mcp-2221: prevent UAF in delayed work

If the device is plugged/unplugged without giving time for mcp_init_work()
to complete, we might kick in the devm free code path and thus have
unavailable struct mcp_2221 while in delayed work.

Canceling the delayed_work item is enough to solve the issue, because
cancel_delayed_work_sync will prevent the work item to requeue itself.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
---
Similar to Pietro's series, we can see the pattern in hid-mcp2221,
except that this time the ledclass is not involved.

Link: https://lore.kernel.org/linux-input/20230125-hid-unregister-leds-v4-5-7860c5763c38@diag.uniroma1.it/
---
Changes in v2:
- drop the spinlock/boolean
- Link to v1: https://lore.kernel.org/r/20230215-wip-mcp2221-v1-1-d7d1da261a5c@redhat.com
---
 drivers/hid/hid-mcp2221.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
index e61dd039354b..f74a977cf8f8 100644
--- a/drivers/hid/hid-mcp2221.c
+++ b/drivers/hid/hid-mcp2221.c
@@ -922,6 +922,9 @@ static void mcp2221_hid_unregister(void *ptr)
 /* This is needed to be sure hid_hw_stop() isn't called twice by the subsystem */
 static void mcp2221_remove(struct hid_device *hdev)
 {
+	struct mcp2221 *mcp = hid_get_drvdata(hdev);
+
+	cancel_delayed_work_sync(&mcp->init_work);
 }
 
 #if IS_REACHABLE(CONFIG_IIO)

---
base-commit: d883fd110dc17308a1506c5bf17e00ce9fe7b2a2
change-id: 20230215-wip-mcp2221-979d4115efb5

Best regards,
-- 
Benjamin Tissoires <benjamin.tissoires@...hat.com>