[PATCH 6.0 075/157] drm/shmem-helper: Remove errant put in error path

Greg Kroah-Hartman
2022-12-12T13:40:11Z

From: Rob Clark <robdclark@chromium.org>

commit 24013314be6ee4ee456114a671e9fa3461323de8 upstream.

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>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221130185748.357410-2-robdclark@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

--- 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_sh
}

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);