[PATCH v5 15/15] media: rc: Fix use after free in bpf progs

[Sean Young]

Since commit dccc0c3ddf8f ("media: rc: fix race between unregister and
urb/irq callbacks"), rcdev->raw is no longer set to NULL after device
unregister. raw->progs could point to stale data.

Fixes: dccc0c3ddf8f ("media: rc: fix race between unregister and urb/irq callbacks")
Signed-off-by: Sean Young <sean@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 drivers/media/rc/bpf-lirc.c  | 18 +++++++++++++-----
 drivers/media/rc/rc-ir-raw.c | 11 +++--------
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/drivers/media/rc/bpf-lirc.c b/drivers/media/rc/bpf-lirc.c
index 2f7564f26445..14ab611e7445 100644
--- a/drivers/media/rc/bpf-lirc.c
+++ b/drivers/media/rc/bpf-lirc.c
@@ -148,12 +148,13 @@ static int lirc_bpf_attach(struct rc_dev *rcdev, struct bpf_prog *prog)
 	if (ret)
 		return ret;
 
-	raw = rcdev->raw;
-	if (!raw) {
+	if (!rcdev->registered) {
 		ret = -ENODEV;
 		goto unlock;
 	}
 
+	raw = rcdev->raw;
+
 	old_array = lirc_rcu_dereference(raw->progs);
 	if (old_array && bpf_prog_array_length(old_array) >= BPF_MAX_PROGS) {
 		ret = -E2BIG;
@@ -186,12 +187,13 @@ static int lirc_bpf_detach(struct rc_dev *rcdev, struct bpf_prog *prog)
 	if (ret)
 		return ret;
 
-	raw = rcdev->raw;
-	if (!raw) {
+	if (!rcdev->registered) {
 		ret = -ENODEV;
 		goto unlock;
 	}
 
+	raw = rcdev->raw;
+
 	old_array = lirc_rcu_dereference(raw->progs);
 	ret = bpf_prog_array_copy(old_array, prog, NULL, 0, &new_array);
 	/*
@@ -235,7 +237,8 @@ void lirc_bpf_free(struct rc_dev *rcdev)
 	struct bpf_prog_array_item *item;
 	struct bpf_prog_array *array;
 
-	array = lirc_rcu_dereference(rcdev->raw->progs);
+	array = rcu_replace_pointer(rcdev->raw->progs, NULL,
+				    lockdep_is_held(&ir_raw_handler_lock));
 	if (!array)
 		return;
 
@@ -316,6 +319,11 @@ int lirc_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
 	if (ret)
 		goto put;
 
+	if (!rcdev->registered) {
+		ret = -ENODEV;
+		goto unlock;
+	}
+
 	progs = lirc_rcu_dereference(rcdev->raw->progs);
 	cnt = progs ? bpf_prog_array_length(progs) : 0;
 
diff --git a/drivers/media/rc/rc-ir-raw.c b/drivers/media/rc/rc-ir-raw.c
index 86de1b26731d..54b323becb1f 100644
--- a/drivers/media/rc/rc-ir-raw.c
+++ b/drivers/media/rc/rc-ir-raw.c
@@ -632,8 +632,11 @@ void ir_raw_event_free(struct rc_dev *dev)
 {
 	if (dev->raw) {
 		timer_delete_sync(&dev->raw->edge_handle);
+		mutex_lock(&ir_raw_handler_lock);
 		if (dev->raw->thread)
 			put_task_struct(dev->raw->thread);
+		lirc_bpf_free(dev);
+		mutex_unlock(&ir_raw_handler_lock);
 		kfree(dev->raw);
 		dev->raw = NULL;
 	}
@@ -643,9 +646,6 @@ void ir_raw_event_unregister(struct rc_dev *dev)
 {
 	struct ir_raw_handler *handler;
 
-	if (!dev || !dev->raw)
-		return;
-
 	/*
 	 * After ir_raw_event_unregister() is called, an sync
 	 * call to ir_raw_event_handle() can still arrive. This function
@@ -665,11 +665,6 @@ void ir_raw_event_unregister(struct rc_dev *dev)
 
 	lirc_bpf_free(dev);
 
-	/*
-	 * A user can be calling bpf(BPF_PROG_{QUERY|ATTACH|DETACH}), so
-	 * ensure that the raw member is null on unlock; this is how
-	 * "device gone" is checked.
-	 */
 	mutex_unlock(&ir_raw_handler_lock);
 }
 
-- 
2.55.0