[PATCH v2] media: iris: fix use-after-free of fmt_src during MBPF check

[Vishnu Reddy]

During concurrency testing, multiple instances can run in parallel, and
each instance uses its own inst->lock while the global core->lock
protects the list of active instances. The race happens because these
locks cover different scopes, inst->lock protects only the internals of
a single instance, while the MBPF checker walks the core list under
core->lock and reads fields like fmt_src->width and fmt_src->height.
At the same time, iris_close() may free fmt_src and fmt_dst under
inst->lock while the instance is still present in the core list. This
allows a situation where the MBPF checker, still iterating through the
core list, reaches an instance whose fmt_src was already freed by another
thread and ends up dereferencing a dangling pointer, resulting in a
use-after-free. This happens because the MBPF checker assumes that any
instance in the core list is fully valid, but the freeing of fmt_src and
fmt_dst without removing the instance from the core list is not correct.

The correct ordering is to defer freeing fmt_src and fmt_dst until after
the instance has been removed from the core list and all teardown under
the core lock has completed, ensuring that no dangling pointers are ever
exposed during MBPF checks.

Fixes: 5ad964ad5656 ("media: iris: Initialize and deinitialize encoder instance structure")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Vishnu Reddy <busanna.reddy@xxxxxxxxxxxxxxxx>
---
Changes in v2:
- Updated the commit description
- Added Fixes tag and Cc stable
- Link to v1: https://lore.kernel.org/r/20260227-fix-use-after-free-of-fmt_src-during-mbpf-v1-1-307cdafffa2a@xxxxxxxxxxxxxxxx
---
 drivers/media/platform/qcom/iris/iris_vdec.c | 6 ------
 drivers/media/platform/qcom/iris/iris_vdec.h | 1 -
 drivers/media/platform/qcom/iris/iris_venc.c | 6 ------
 drivers/media/platform/qcom/iris/iris_venc.h | 1 -
 drivers/media/platform/qcom/iris/iris_vidc.c | 6 ++----
 5 files changed, 2 insertions(+), 18 deletions(-)

diff --git a/drivers/media/platform/qcom/iris/iris_vdec.c b/drivers/media/platform/qcom/iris/iris_vdec.c
index 719217399a30..99d544e2af4f 100644
--- a/drivers/media/platform/qcom/iris/iris_vdec.c
+++ b/drivers/media/platform/qcom/iris/iris_vdec.c
@@ -61,12 +61,6 @@ int iris_vdec_inst_init(struct iris_inst *inst)
 	return iris_ctrls_init(inst);
 }
 
-void iris_vdec_inst_deinit(struct iris_inst *inst)
-{
-	kfree(inst->fmt_dst);
-	kfree(inst->fmt_src);
-}
-
 static const struct iris_fmt iris_vdec_formats_cap[] = {
 	[IRIS_FMT_NV12] = {
 		.pixfmt = V4L2_PIX_FMT_NV12,
diff --git a/drivers/media/platform/qcom/iris/iris_vdec.h b/drivers/media/platform/qcom/iris/iris_vdec.h
index ec1ce55d1375..5123d2a340e1 100644
--- a/drivers/media/platform/qcom/iris/iris_vdec.h
+++ b/drivers/media/platform/qcom/iris/iris_vdec.h
@@ -9,7 +9,6 @@
 struct iris_inst;
 
 int iris_vdec_inst_init(struct iris_inst *inst);
-void iris_vdec_inst_deinit(struct iris_inst *inst);
 int iris_vdec_enum_fmt(struct iris_inst *inst, struct v4l2_fmtdesc *f);
 int iris_vdec_try_fmt(struct iris_inst *inst, struct v4l2_format *f);
 int iris_vdec_s_fmt(struct iris_inst *inst, struct v4l2_format *f);
diff --git a/drivers/media/platform/qcom/iris/iris_venc.c b/drivers/media/platform/qcom/iris/iris_venc.c
index aa27b22704eb..4d886769d958 100644
--- a/drivers/media/platform/qcom/iris/iris_venc.c
+++ b/drivers/media/platform/qcom/iris/iris_venc.c
@@ -79,12 +79,6 @@ int iris_venc_inst_init(struct iris_inst *inst)
 	return iris_ctrls_init(inst);
 }
 
-void iris_venc_inst_deinit(struct iris_inst *inst)
-{
-	kfree(inst->fmt_dst);
-	kfree(inst->fmt_src);
-}
-
 static const struct iris_fmt iris_venc_formats_cap[] = {
 	[IRIS_FMT_H264] = {
 		.pixfmt = V4L2_PIX_FMT_H264,
diff --git a/drivers/media/platform/qcom/iris/iris_venc.h b/drivers/media/platform/qcom/iris/iris_venc.h
index c4db7433da53..00c1716b2747 100644
--- a/drivers/media/platform/qcom/iris/iris_venc.h
+++ b/drivers/media/platform/qcom/iris/iris_venc.h
@@ -9,7 +9,6 @@
 struct iris_inst;
 
 int iris_venc_inst_init(struct iris_inst *inst);
-void iris_venc_inst_deinit(struct iris_inst *inst);
 int iris_venc_enum_fmt(struct iris_inst *inst, struct v4l2_fmtdesc *f);
 int iris_venc_try_fmt(struct iris_inst *inst, struct v4l2_format *f);
 int iris_venc_s_fmt(struct iris_inst *inst, struct v4l2_format *f);
diff --git a/drivers/media/platform/qcom/iris/iris_vidc.c b/drivers/media/platform/qcom/iris/iris_vidc.c
index bd38d84c9cc7..5eb1786b0737 100644
--- a/drivers/media/platform/qcom/iris/iris_vidc.c
+++ b/drivers/media/platform/qcom/iris/iris_vidc.c
@@ -289,10 +289,6 @@ int iris_close(struct file *filp)
 	v4l2_m2m_ctx_release(inst->m2m_ctx);
 	v4l2_m2m_release(inst->m2m_dev);
 	mutex_lock(&inst->lock);
-	if (inst->domain == DECODER)
-		iris_vdec_inst_deinit(inst);
-	else if (inst->domain == ENCODER)
-		iris_venc_inst_deinit(inst);
 	iris_session_close(inst);
 	iris_inst_change_state(inst, IRIS_INST_DEINIT);
 	iris_v4l2_fh_deinit(inst, filp);
@@ -304,6 +300,8 @@ int iris_close(struct file *filp)
 	mutex_unlock(&inst->lock);
 	mutex_destroy(&inst->ctx_q_lock);
 	mutex_destroy(&inst->lock);
+	kfree(inst->fmt_src);
+	kfree(inst->fmt_dst);
 	kfree(inst);
 
 	return 0;

---
base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
change-id: 20260226-fix-use-after-free-of-fmt_src-during-mbpf-abc27f573400

Best regards,
-- 
Vishnu Reddy <busanna.reddy@xxxxxxxxxxxxxxxx>