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From:   Qiujun Huang <hqjagain@gmail.com>
Date:   Mon, 16 Mar 2020 15:15:46 +0800
Message-ID: <CAJRQjofA4+LJxYn-HQdBZ_Lxv3DgS1WrPtM3L1z4-ycRKPS5nw@mail.gmail.com>
Subject: Re: [PATCH] drm/lease: fix potential race in fill_object_idr
To:     vyasevich@gmail.com, nhorman@tuxdriver.com,
        marcelo.leitner@gmail.com, "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>
Cc:     linux-sctp@vger.kernel.org, netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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Sorry about sending to wrong maintainers. Please ignore it.
I'll resend it.

On Mon, Mar 16, 2020 at 2:59 PM Qiujun Huang <hqjagain@gmail.com> wrote:
>
> We should hold idr_mutex for idr_alloc.
>
> Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
> ---
>  drivers/gpu/drm/drm_lease.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c
> index b481caf..427ee21 100644
> --- a/drivers/gpu/drm/drm_lease.c
> +++ b/drivers/gpu/drm/drm_lease.c
> @@ -418,6 +418,7 @@ static int fill_object_idr(struct drm_device *dev,
>                 goto out_free_objects;
>         }
>
> +       mutex_lock(&dev->mode_config.idr_mutex);
>         /* add their IDs to the lease request - taking into account
>            universal planes */
>         for (o = 0; o < object_count; o++) {
> @@ -437,7 +438,7 @@ static int fill_object_idr(struct drm_device *dev,
>                 if (ret < 0) {
>                         DRM_DEBUG_LEASE("Object %d cannot be inserted into leases (%d)\n",
>                                         object_id, ret);
> -                       goto out_free_objects;
> +                       goto out_unlock;
>                 }
>                 if (obj->type == DRM_MODE_OBJECT_CRTC && !universal_planes) {
>                         struct drm_crtc *crtc = obj_to_crtc(obj);
> @@ -445,20 +446,22 @@ static int fill_object_idr(struct drm_device *dev,
>                         if (ret < 0) {
>                                 DRM_DEBUG_LEASE("Object primary plane %d cannot be inserted into leases (%d)\n",
>                                                 object_id, ret);
> -                               goto out_free_objects;
> +                               goto out_unlock;
>                         }
>                         if (crtc->cursor) {
>                                 ret = idr_alloc(leases, &drm_lease_idr_object, crtc->cursor->base.id, crtc->cursor->base.id + 1, GFP_KERNEL);
>                                 if (ret < 0) {
>                                         DRM_DEBUG_LEASE("Object cursor plane %d cannot be inserted into leases (%d)\n",
>                                                         object_id, ret);
> -                                       goto out_free_objects;
> +                                       goto out_unlock;
>                                 }
>                         }
>                 }
>         }
>
>         ret = 0;
> +out_unlock:
> +       mutex_unlock(&dev->mode_config.idr_mutex);
>  out_free_objects:
>         for (o = 0; o < object_count; o++) {
>                 if (objects[o])
> --
> 1.8.3.1
>