[PATCH] soc: qcom: pmic_glink_altmode: Fix use-after-free of work items on unbind

[Abel Vesa]

The altmode context, including the enable_work and the per-port work
items, is devm-allocated, but nothing cancels the work items on unbind.
A PDR or GLINK notification can queue them on the system workqueues, so
if the device gets unbound while one is pending or running, devres frees
the context, the typec handles and the pmic_glink client under it, and
the worker then dereferences freed memory.

Cancelling the work items is not enough on its own, since the client
callbacks keep queueing them until the client devres is released. So
register a devm action, right after the client is allocated, which
disables the works using disable_work_sync(). Devres runs actions in
reverse order, so on unbind this happens first, waiting for any running
worker while the client, typec handles and bridges are still around,
and making any later queueing from the client callbacks a no-op.

Fixes: 080b4e24852b ("soc: qcom: pmic_glink: Introduce altmode support")
Cc: stable@xxxxxxxxxxxxxxx # 6.10
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://sashiko.dev/#/bug/linux-762f89d1-07b0-45e1-9557-bf643a826aa1
Signed-off-by: Abel Vesa <abel.vesa@xxxxxxxxxxxxxxxx>
---
Prepared with help from an LLM-based assistant.
---
 drivers/soc/qcom/pmic_glink_altmode.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/soc/qcom/pmic_glink_altmode.c b/drivers/soc/qcom/pmic_glink_altmode.c
index 465e5d2316a0..3f6d3290d29b 100644
--- a/drivers/soc/qcom/pmic_glink_altmode.c
+++ b/drivers/soc/qcom/pmic_glink_altmode.c
@@ -543,6 +543,23 @@ static void pmic_glink_altmode_put_switch(void *data)
 	typec_switch_put(data);
 }
 
+static void pmic_glink_altmode_disable_work(void *data)
+{
+	struct pmic_glink_altmode *altmode = data;
+	struct pmic_glink_altmode_port *alt_port;
+	unsigned int port;
+
+	disable_work_sync(&altmode->enable_work);
+
+	for (port = 0; port < ARRAY_SIZE(altmode->ports); port++) {
+		alt_port = &altmode->ports[port];
+		if (!alt_port->altmode)
+			continue;
+
+		disable_work_sync(&alt_port->work);
+	}
+}
+
 static void pmic_glink_altmode_enable_worker(struct work_struct *work)
 {
 	struct pmic_glink_altmode *altmode = work_to_altmode(work);
@@ -695,6 +712,18 @@ static int pmic_glink_altmode_probe(struct auxiliary_device *adev,
 	if (IS_ERR(altmode->client))
 		return PTR_ERR(altmode->client);
 
+	/*
+	 * Registered after the client, so that on unbind the workers are
+	 * disabled, and any in-flight instance is waited for, before the
+	 * client, the typec handles and the altmode context go away. The
+	 * client callbacks may still fire until the client is released, so
+	 * disable rather than cancel the works to keep them from being
+	 * requeued.
+	 */
+	ret = devm_add_action_or_reset(dev, pmic_glink_altmode_disable_work, altmode);
+	if (ret)
+		return ret;
+
 	pmic_glink_client_register(altmode->client);
 
 	return 0;

---
base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
change-id: 20261102-pmic-glink-altmode-teardown-uaf-8ccf631de17f

Best regards,
--  

Abel