[PATCH v2 2/5] media: iris: take core lock when scanning the instance list

[Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>]

iris_check_session_supported() walks core->instances to confirm the
current instance is registered, but does so without holding core->lock.
A concurrent iris_close() takes core->lock and removes a (possibly
different) instance from the list via list_del_init() before freeing it,
so the lockless traversal can follow a freed pointer and dereference it,
resulting in a use-after-free.

Hold core->lock across the list traversal, matching the other iterators
over core->instances such as iris_check_core_mbpf(). The lock is dropped
before iris_check_core_mbpf() is called so the nesting is unchanged.

Fixes: bdbe1cac0c10 ("media: iris: add check whether the video session is supported or not")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/media/platform/qcom/iris/iris_vb2.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/qcom/iris/iris_vb2.c b/drivers/media/platform/qcom/iris/iris_vb2.c
index a2ea2d67f60d..8faf709c26c1 100644
--- a/drivers/media/platform/qcom/iris/iris_vb2.c
+++ b/drivers/media/platform/qcom/iris/iris_vb2.c
@@ -56,10 +56,14 @@ static int iris_check_session_supported(struct iris_inst *inst)
 	bool found = false;
 	int ret;
 
+	mutex_lock(&core->lock);
 	list_for_each_entry(instance, &core->instances, list) {
-		if (instance == inst)
+		if (instance == inst) {
 			found = true;
+			break;
+		}
 	}
+	mutex_unlock(&core->lock);
 
 	if (!found) {
 		ret = -EINVAL;

-- 
2.47.3