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@redhat.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@redhat.com>

On Thu, 16 Feb 2023 11:22:58 +0100, Benjamin Tissoires wrote:
> 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.
> 
> [...]

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/hid/hid.git (for-6.3/mcp2221), thanks!

[1/1] HID: mcp-2221: prevent UAF in delayed work
      https://git.kernel.org/hid/hid/c/47e91fdfa511

Cheers,
-- 
Benjamin Tissoires <benjamin.tissoires@redhat.com>

On Thu, 16 Feb 2023, Benjamin Tissoires wrote:

> 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@redhat.com>

Acked-by: Jiri Kosina <jkosina@suse.cz>

Thanks Benjamin.

-- 
Jiri Kosina
SUSE Labs

On Mon, Feb 20, 2023 at 10:10 AM Jiri Kosina <jikos@kernel.org> wrote:
>
> On Thu, 16 Feb 2023, Benjamin Tissoires wrote:
>
> > 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@redhat.com>
>
> Acked-by: Jiri Kosina <jkosina@suse.cz>

Thanks a lot.
I realized I was missing the Fixes 960f9df7c620 and Cc: stable tags.

I am adding those right now and will push it as soon as the minimum CI
reports back that it's OK.

Cheers,
Benjamin

>
> Thanks Benjamin.
>
> --
> Jiri Kosina
> SUSE Labs
>