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    Subject[76/90] drm/i915: Avoid NULL dereference with component_only tv_modes
    2.6.31-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Chris Wilson <chris@chris-wilson.co.uk>

    commit d271817baecbccb47da0d9f28c285a0dae8a06b7 upstream.

    In commit d2d9f2324, the guard for a valid video mode was removed. This
    caused the regression:

    kernel crash during kms graphic boot on Intel GM4500 platform
    https://bugzilla.redhat.com/show_bug.cgi?id=540218

    This patches changes the logic slightly not to rely on a coupled
    variable, but to just check whether the video_modes is valid before
    dereferencing.

    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: David Woodhouse <dwmw2@infradead.org>
    Cc: Zhenyu Wang <zhenyu.z.wang@intel.com>
    [ickle: Actually reference the correct bug report]
    Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
    Signed-off-by: Eric Anholt <eric@anholt.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/gpu/drm/i915/intel_tv.c | 11 ++++-------
    1 file changed, 4 insertions(+), 7 deletions(-)

    --- a/drivers/gpu/drm/i915/intel_tv.c
    +++ b/drivers/gpu/drm/i915/intel_tv.c
    @@ -1212,20 +1212,17 @@ intel_tv_mode_set(struct drm_encoder *en
    tv_ctl |= TV_TRILEVEL_SYNC;
    if (tv_mode->pal_burst)
    tv_ctl |= TV_PAL_BURST;
    +
    scctl1 = 0;
    - /* dda1 implies valid video levels */
    - if (tv_mode->dda1_inc) {
    + if (tv_mode->dda1_inc)
    scctl1 |= TV_SC_DDA1_EN;
    - }
    -
    if (tv_mode->dda2_inc)
    scctl1 |= TV_SC_DDA2_EN;
    -
    if (tv_mode->dda3_inc)
    scctl1 |= TV_SC_DDA3_EN;
    -
    scctl1 |= tv_mode->sc_reset;
    - scctl1 |= video_levels->burst << TV_BURST_LEVEL_SHIFT;
    + if (video_levels)
    + scctl1 |= video_levels->burst << TV_BURST_LEVEL_SHIFT;
    scctl1 |= tv_mode->dda1_inc << TV_SCDDA1_INC_SHIFT;

    scctl2 = tv_mode->dda2_size << TV_SCDDA2_SIZE_SHIFT |



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