[PATCH v1 3/6] udmabuf: Assert held reservation lock for dma-buf mmapping

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

When userspace mmaps dma-buf's fd, the dma-buf reservation lock must be
held. Add locking sanity check to the dma-buf mmaping callback to ensure
that the locking assumption won't regress in the future.

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 drivers/dma-buf/udmabuf.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 2bcdb935a3ac..283816fbd72f 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -2,6 +2,7 @@
 #include <linux/cred.h>
 #include <linux/device.h>
 #include <linux/dma-buf.h>
+#include <linux/dma-resv.h>
 #include <linux/highmem.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -49,6 +50,8 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
 {
 	struct udmabuf *ubuf = buf->priv;
 
+	dma_resv_assert_held(buf->resv);
+
 	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
 		return -EINVAL;
 
-- 
2.37.3