[PATCH] staging: media: meson: vdec: fix UAF, memory leak and NULL derefs

[Alfie Varghese]

This combined commit fixes several pre-existing issues identified in the
Amlogic video decoder driver:

1. Fix a critical Use-After-Free in vdec_close() by synchronously
   canceling the sess->esparser_queue_work before freeing the session.
2. Fix a memory leak in vdec_close() by freeing the session control
   handler via v4l2_ctrl_handler_free().
3. Prevent a potential NULL pointer dereference in vdec_probe() by adding
   a NULL check for of_match_node()'s return value.
4. Prevent a potential NULL pointer dereference in vdec_isr() and
   vdec_threaded_isr() by adding NULL checks for core->cur_sess.

Signed-off-by: Alfie Varghese <alfievarghese22@xxxxxxxxx>
---
 drivers/staging/media/meson/vdec/vdec.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/staging/media/meson/vdec/vdec.c b/drivers/staging/media/meson/vdec/vdec.c
index a039d925c0fe..b794ad53711c 100644
--- a/drivers/staging/media/meson/vdec/vdec.c
+++ b/drivers/staging/media/meson/vdec/vdec.c
@@ -926,11 +926,15 @@ static int vdec_close(struct file *file)
 {
 	struct amvdec_session *sess = file_to_amvdec_session(file);
 
+	cancel_work_sync(&sess->esparser_queue_work);
+
 	v4l2_m2m_ctx_release(sess->m2m_ctx);
 	v4l2_m2m_release(sess->m2m_dev);
 	v4l2_fh_del(&sess->fh, file);
 	v4l2_fh_exit(&sess->fh);
 
+	v4l2_ctrl_handler_free(&sess->ctrl_handler);
+
 	mutex_destroy(&sess->lock);
 	mutex_destroy(&sess->bufs_recycle_lock);
 
@@ -953,6 +957,9 @@ static irqreturn_t vdec_isr(int irq, void *data)
 	struct amvdec_core *core = data;
 	struct amvdec_session *sess = core->cur_sess;
 
+	if (!sess)
+		return IRQ_NONE;
+
 	sess->last_irq_jiffies = get_jiffies_64();
 
 	return sess->fmt_out->codec_ops->isr(sess);
@@ -963,6 +970,9 @@ static irqreturn_t vdec_threaded_isr(int irq, void *data)
 	struct amvdec_core *core = data;
 	struct amvdec_session *sess = core->cur_sess;
 
+	if (!sess)
+		return IRQ_NONE;
+
 	return sess->fmt_out->codec_ops->threaded_isr(sess);
 }
 
@@ -1020,6 +1030,8 @@ static int vdec_probe(struct platform_device *pdev)
 		return PTR_ERR(core->canvas);
 
 	of_id = of_match_node(vdec_dt_match, dev->of_node);
+	if (!of_id)
+		return -ENODEV;
 	core->platform = of_id->data;
 
 	if (core->platform->revision == VDEC_REVISION_G12A ||