On 11/30/22 21:57, Rob Clark wrote:
From: Rob Clark robdclark@chromium.org
drm_gem_shmem_mmap() doesn't own this reference, resulting in the GEM object getting prematurely freed leading to a later use-after-free.
Link: https://syzkaller.appspot.com/bug?extid=c8ae65286134dd1b800d Reported-by: syzbot+c8ae65286134dd1b800d@syzkaller.appspotmail.com Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects") Cc: stable@vger.kernel.org Signed-off-by: Rob Clark robdclark@chromium.org Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
drivers/gpu/drm/drm_gem_shmem_helper.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 35138f8a375c..3b7b71391a4c 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -622,10 +622,8 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct } ret = drm_gem_shmem_get_pages(shmem);
- if (ret) {
drm_gem_vm_close(vma);
- if (ret) return ret;
- }
vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
AFAICS, the dmabuf mmaping code path needs a similar fix, isn't it?
- /* Drop the reference drm_gem_mmap_obj() acquired.*/ - drm_gem_object_put(obj); vma->vm_private_data = NULL;
- return dma_buf_mmap(obj->dma_buf, vma, 0); + ret = dma_buf_mmap(obj->dma_buf, vma, 0); + + /* Drop the reference drm_gem_mmap_obj() acquired.*/ + if (!ret) + drm_gem_object_put(obj); + + return ret;