[PATCH v2 4/5] media: iris: reject open() when the session limit is reached

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

iris_add_session() silently skips adding the instance to core->instances
once max_session_count is reached, but returns void, so iris_open()
continues as if it succeeded and hands a file descriptor back to
userspace. As the instance is not on core->instances, firmware responses
for it are dropped and every subsequent ioctl times out.

Make iris_add_session() return an error when the limit is reached and
fail iris_open() accordingly, freeing the partially initialised instance.

Fixes: 38fc8beaba55 ("media: iris: implement reqbuf ioctl with vb2_queue_setup")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/media/platform/qcom/iris/iris_vidc.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/media/platform/qcom/iris/iris_vidc.c b/drivers/media/platform/qcom/iris/iris_vidc.c
index fcbc60016bee..4ca9185b3d2b 100644
--- a/drivers/media/platform/qcom/iris/iris_vidc.c
+++ b/drivers/media/platform/qcom/iris/iris_vidc.c
@@ -40,21 +40,23 @@ static void iris_v4l2_fh_deinit(struct iris_inst *inst, struct file *filp)
 	v4l2_fh_exit(&inst->fh);
 }
 
-static void iris_add_session(struct iris_inst *inst)
+static int iris_add_session(struct iris_inst *inst)
 {
 	struct iris_core *core = inst->core;
 	struct iris_inst *iter;
 	u32 count = 0;
 
-	mutex_lock(&core->lock);
+	guard(mutex)(&core->lock);
 
 	list_for_each_entry(iter, &core->instances, list)
 		count++;
 
-	if (count < core->iris_platform_data->max_session_count)
-		list_add_tail(&inst->list, &core->instances);
+	if (count >= core->iris_platform_data->max_session_count)
+		return -EBUSY;
 
-	mutex_unlock(&core->lock);
+	list_add_tail(&inst->list, &core->instances);
+
+	return 0;
 }
 
 static void iris_remove_session(struct iris_inst *inst)
@@ -206,12 +208,17 @@ int iris_open(struct file *filp)
 	if (ret)
 		goto fail_m2m_ctx_release;
 
-	iris_add_session(inst);
+	ret = iris_add_session(inst);
+	if (ret)
+		goto fail_inst_deinit;
 
 	inst->fh.m2m_ctx = inst->m2m_ctx;
 
 	return 0;
 
+fail_inst_deinit:
+	kfree(inst->fmt_src);
+	kfree(inst->fmt_dst);
 fail_m2m_ctx_release:
 	v4l2_m2m_ctx_release(inst->m2m_ctx);
 fail_m2m_release:

-- 
2.47.3