The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8b917cbe38e9b0d002492477a9fc2bfee2412ce4 Mon Sep 17 00:00:00 2001 From: Xiaomeng Tong xiam0nd.tong@gmail.com Date: Sun, 27 Mar 2022 14:15:16 +0800 Subject: [PATCH] tilcdc: tilcdc_external: fix an incorrect NULL check on list iterator

The bug is here: if (!encoder) {

The list iterator value 'encoder' will *always* be set and non-NULL by list_for_each_entry(), so it is incorrect to assume that the iterator value will be NULL if the list is empty or no element is found.

To fix the bug, use a new variable 'iter' as the list iterator, while use the original variable 'encoder' as a dedicated pointer to point to the found element.

Cc: stable@vger.kernel.org Fixes: ec9eab097a500 ("drm/tilcdc: Add drm bridge support for attaching drm bridge drivers") Signed-off-by: Xiaomeng Tong xiam0nd.tong@gmail.com Reviewed-by: Jyri Sarha jyri.sarha@iki.fi Tested-by: Jyri Sarha jyri.sarha@iki.fi Signed-off-by: Jyri Sarha jyri.sarha@iki.fi Link: https://patchwork.freedesktop.org/patch/msgid/20220327061516.5076-1-xiam0nd....

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_external.c b/drivers/gpu/drm/tilcdc/tilcdc_external.c index 7594cf6e186e..3b86d002ef62 100644 --- a/drivers/gpu/drm/tilcdc/tilcdc_external.c +++ b/drivers/gpu/drm/tilcdc/tilcdc_external.c @@ -60,11 +60,13 @@ struct drm_connector *tilcdc_encoder_find_connector(struct drm_device *ddev, int tilcdc_add_component_encoder(struct drm_device *ddev) { struct tilcdc_drm_private *priv = ddev->dev_private; - struct drm_encoder *encoder; + struct drm_encoder *encoder = NULL, *iter;

- list_for_each_entry(encoder, &ddev->mode_config.encoder_list, head) - if (encoder->possible_crtcs & (1 << priv->crtc->index)) + list_for_each_entry(iter, &ddev->mode_config.encoder_list, head) + if (iter->possible_crtcs & (1 << priv->crtc->index)) { + encoder = iter; break; + }

if (!encoder) { dev_err(ddev->dev, "%s: No suitable encoder found\n", __func__);