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SubjectRe: [PATCH] dpu1: dpu_encoder: fix a missing check on list iterator
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On 27/03/2022 10:32, Xiaomeng Tong wrote:
> The bug is here:
> cstate = to_dpu_crtc_state(drm_crtc->state);
>
> For the drm_for_each_crtc(), just like list_for_each_entry(),
> the list iterator 'drm_crtc' will point to a bogus position
> containing HEAD if the list is empty or no element is found.
> This case must be checked before any use of the iterator,
> otherwise it will lead to a invalid memory access.
>
> To fix this bug, use a new variable 'iter' as the list iterator,
> while use the origin variable 'drm_crtc' as a dedicated pointer
> to point to the found element.
>
> Cc: stable@vger.kernel.org
> Fixes: b107603b4ad0f ("drm/msm/dpu: map mixer/ctl hw blocks in encoder modeset")
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 1e648db439f9..d3fdb18e96f9 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -965,7 +965,7 @@ static void dpu_encoder_virt_mode_set(struct drm_encoder *drm_enc,
> struct dpu_kms *dpu_kms;
> struct list_head *connector_list;
> struct drm_connector *conn = NULL, *conn_iter;
> - struct drm_crtc *drm_crtc;
> + struct drm_crtc *drm_crtc = NULL, *iter;
> struct dpu_crtc_state *cstate;
> struct dpu_global_state *global_state;
> struct dpu_hw_blk *hw_pp[MAX_CHANNELS_PER_ENC];
> @@ -1007,9 +1007,14 @@ static void dpu_encoder_virt_mode_set(struct drm_encoder *drm_enc,
> return;
> }
>
> - drm_for_each_crtc(drm_crtc, drm_enc->dev)
> - if (drm_crtc->state->encoder_mask & drm_encoder_mask(drm_enc))
> + drm_for_each_crtc(iter, drm_enc->dev)
> + if (iter->state->encoder_mask & drm_encoder_mask(drm_enc)) {
> + drm_crtc = iter;
> break;
> + }
> +
> + if (!drm_crtc)
> + return;
>
> /* Query resource that have been reserved in atomic check step. */
> num_pp = dpu_rm_get_assigned_resources(&dpu_kms->rm, global_state,


--
With best wishes
Dmitry

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