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    Subject[PATCH 5.18 844/879] tilcdc: tilcdc_external: fix an incorrect NULL check on list iterator
    Date
    From: Xiaomeng Tong <xiam0nd.tong@gmail.com>

    commit 8b917cbe38e9b0d002492477a9fc2bfee2412ce4 upstream.

    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.tong@gmail.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/gpu/drm/tilcdc/tilcdc_external.c | 8 +++++---
    1 file changed, 5 insertions(+), 3 deletions(-)

    --- 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_fin
    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__);

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