[PATCH v1 2/6] drm: Assert held reservation lock for dma-buf mmapping

[Dmitry Osipenko]

When userspace mmaps dma-buf's fd, the dma-buf reservation lock must be
held. Add locking sanity checks to the dma-buf mmaping callbacks of DRM
drivers to ensure that the locking assumptions won't regress in future.

Suggested-by: Daniel Vetter <dan...@ffwll.ch>
Signed-off-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>
---
 drivers/gpu/drm/drm_prime.c                | 2 ++
 drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 2 ++
 drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c  | 2 ++
 drivers/gpu/drm/tegra/gem.c                | 2 ++
 4 files changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 20e109a802ae..f924b8b4ab6b 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -781,6 +781,8 @@ int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct 
vm_area_struct *vma)
        struct drm_gem_object *obj = dma_buf->priv;
        struct drm_device *dev = obj->dev;
 
+       dma_resv_assert_held(dma_buf->resv);
+
        if (!dev->driver->gem_prime_mmap)
                return -ENOSYS;
 
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c 
b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
index ec6f7ae47783..9322ac29008b 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
@@ -97,6 +97,8 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, 
struct vm_area_struct *
        struct drm_i915_private *i915 = to_i915(obj->base.dev);
        int ret;
 
+       dma_resv_assert_held(dma_buf->resv);
+
        if (obj->base.size < vma->vm_end - vma->vm_start)
                return -EINVAL;
 
diff --git a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c 
b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
index 8e194dbc9506..3abc47521b2c 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
@@ -66,6 +66,8 @@ static int omap_gem_dmabuf_mmap(struct dma_buf *buffer,
        struct drm_gem_object *obj = buffer->priv;
        int ret = 0;
 
+       dma_resv_assert_held(buffer->resv);
+
        ret = drm_gem_mmap_obj(obj, omap_gem_mmap_size(obj), vma);
        if (ret < 0)
                return ret;
diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index b09b8ab40ae4..979e7bc902f6 100644
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -694,6 +694,8 @@ static int tegra_gem_prime_mmap(struct dma_buf *buf, struct 
vm_area_struct *vma)
        struct drm_gem_object *gem = buf->priv;
        int err;
 
+       dma_resv_assert_held(buf->resv);
+
        err = drm_gem_mmap_obj(gem, gem->size, vma);
        if (err < 0)
                return err;
-- 
2.37.3