From: Jonathan Gonzalez V zeus@gnu.org

Performing vma lookups without taking the mm->mmap_sem is asking for trouble. While doing the search, the vma in question can be modified or even removed before returning to the caller. Take the lock (exclusively) in order to avoid races while iterating through the vmacache and/or rbtree.

This patch is completely *untested*.

Signed-off-by: Jonathan Gonzalez V zeus@gnu.org Signed-off-by: Davidlohr Bueso davidlohr@hp.com Cc: Inki Dae inki.dae@samsung.com Cc: Joonyoung Shim jy0922.shim@samsung.com Cc: David Airlie airlied@linux.ie Cc: dri-devel@lists.freedesktop.org Cc: linux-samsung-soc@vger.kernel.org --- drivers/gpu/drm/exynos/exynos_drm_g2d.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c index 6c1885e..8001587 100644 --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c @@ -467,14 +467,17 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct drm_device *drm_dev, goto err_free; }

+ down_read(&current->mm->mmap_sem); vma = find_vma(current->mm, userptr); if (!vma) { + up_read(&current->mm->mmap_sem); DRM_ERROR("failed to get vm region.\n"); ret = -EFAULT; goto err_free_pages; }

if (vma->vm_end < userptr + size) { + up_read(&current->mm->mmap_sem); DRM_ERROR("vma is too small.\n"); ret = -EFAULT; goto err_free_pages; @@ -482,6 +485,7 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct drm_device *drm_dev,

g2d_userptr->vma = exynos_gem_get_vma(vma); if (!g2d_userptr->vma) { + up_read(&current->mm->mmap_sem); DRM_ERROR("failed to copy vma.\n"); ret = -ENOMEM; goto err_free_pages; @@ -492,10 +496,12 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct drm_device *drm_dev, ret = exynos_gem_get_pages_from_userptr(start & PAGE_MASK, npages, pages, vma); if (ret < 0) { + up_read(&current->mm->mmap_sem); DRM_ERROR("failed to get user pages from userptr.\n"); goto err_put_vma; }

+ up_read(&current->mm->mmap_sem); g2d_userptr->pages = pages;

sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);