[PATCH v3 06/22] accel: ethosu: Prevent command stream export

[Rob Herring (Arm)]

Command stream BOs are validated at creation time, but the generic PRIME
export path can expose their backing memory to a DMA-BUF importer. The
importer can then modify the command stream before the NPU executes it.

Reject PRIME export for validated command stream BOs while retaining generic
export for data BOs.

Fixes: 5a5e9c0228e6 ("accel: Add Arm Ethos-U NPU driver")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: LLM
Signed-off-by: Rob Herring (Arm) <robh@xxxxxxxxxx>
---
v3:
 - new patch
---
 drivers/accel/ethosu/ethosu_gem.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/accel/ethosu/ethosu_gem.c b/drivers/accel/ethosu/ethosu_gem.c
index 9afe2549ec84..c046aee42687 100644
--- a/drivers/accel/ethosu/ethosu_gem.c
+++ b/drivers/accel/ethosu/ethosu_gem.c
@@ -6,6 +6,7 @@
 #include <linux/slab.h>
 
 #include <drm/ethosu_accel.h>
+#include <drm/drm_prime.h>
 
 #include "ethosu_device.h"
 #include "ethosu_gem.h"
@@ -30,9 +31,18 @@ static int ethosu_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *vm
 	return drm_gem_dma_object_mmap(obj, vma);
 }
 
+static struct dma_buf *ethosu_gem_export(struct drm_gem_object *obj, int flags)
+{
+	if (to_ethosu_bo(obj)->info)
+		return ERR_PTR(-EPERM);
+
+	return drm_gem_prime_export(obj, flags);
+}
+
 static const struct drm_gem_object_funcs ethosu_gem_funcs = {
 	.free = ethosu_gem_free_object,
 	.print_info = drm_gem_dma_object_print_info,
+	.export = ethosu_gem_export,
 	.get_sg_table = drm_gem_dma_object_get_sg_table,
 	.vmap = drm_gem_dma_object_vmap,
 	.mmap = ethosu_gem_mmap,

-- 
2.53.0