Quoting Eric Biggers (2019-02-26 20:47:26)
> From: Eric Biggers <ebigg...@google.com>
>
> If drm_gem_handle_create() fails in vgem_gem_create(), then the
> drm_vgem_gem_object is freed twice: once when the reference is dropped
> by drm_gem_object_put_unlocked(), and again by __vgem_gem_destroy().
>
> This was hit by syzkaller using fault injection.
>
> Fix it by skipping the second free.
>
> Reported-by: syzbot+e73f2fb5ed5a5df36...@syzkaller.appspotmail.com
> Fixes: 5ba6c9ff961a ("drm/vgem: Fix mmaping")
That's the wrong fixes line, it's
Fixes: af33a9190d02 ("drm/vgem: Enable dmabuf import interfaces")
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Laura Abbott <labb...@redhat.com>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Sadly I reviewed it so I'm still culpable, but the fix is correct as the
put purposely frees it on error.
> Cc: sta...@vger.kernel.org
> Signed-off-by: Eric Biggers <ebigg...@google.com>
> ---
> drivers/gpu/drm/vgem/vgem_drv.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index 5930facd6d2d8..70646d9da1596 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -189,15 +189,13 @@ static struct drm_gem_object *vgem_gem_create(struct
> drm_device *dev,
> return ERR_CAST(obj);
>
> ret = drm_gem_handle_create(file, &obj->base, handle);
> +
> drm_gem_object_put_unlocked(&obj->base);
> +
The pattern in the other GEM drivers is not to have these extra
newlines.
Reviewed-by: Chris Wilson <ch...@chris-wilson.co.uk>
> if (ret)
> - goto err;
> + return ERR_PTR(ret);
>
> return &obj->base;
> -
> -err:
> - __vgem_gem_destroy(obj);
> - return ERR_PTR(ret);
> }
>
> static int vgem_gem_dumb_create(struct drm_file *file, struct drm_device
> *dev,
> --
> 2.21.0.rc2.261.ga7da99ff1b-goog
>
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