Re: [PATCH 1/2] drm/i915: Don't attempt to read an unitialized stack value

Daniel Vetter
2013-07-12T15:33:36Z

On Fri, Jul 12, 2013 at 04:24:40PM +0100, Damien Lespiau wrote:
> If intel_sdvo_get_value() fails here, val is unitialized and the cross
> check will compare the pipe config multiplier with a bogus value.
>
> Instead, only set encoder_pixel_multiplier when the sdvo command has
> been successful. The cross check will compare the pipe config value with
> 0 otherwise.
>
> v2: Do the cross check with the initial value of encoder_pixel_multiplier (0)
> if the sdvo command fails (and thus keep the warning) (Daniel Vetter)
>
> Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Queued for -next, thanks for the patch.
-Daniel
> ---
> drivers/gpu/drm/i915/intel_sdvo.c | 24 +++++++++++++-----------
> 1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
> index b8e1623..eb2a603 100644
> --- a/drivers/gpu/drm/i915/intel_sdvo.c
> +++ b/drivers/gpu/drm/i915/intel_sdvo.c
> @@ -1357,17 +1357,19 @@ static void intel_sdvo_get_config(struct intel_encoder *encoder,
> }
>
> /* Cross check the port pixel multiplier with the sdvo encoder state. */
> - intel_sdvo_get_value(intel_sdvo, SDVO_CMD_GET_CLOCK_RATE_MULT, &val, 1);
> - switch (val) {
> - case SDVO_CLOCK_RATE_MULT_1X:
> - encoder_pixel_multiplier = 1;
> - break;
> - case SDVO_CLOCK_RATE_MULT_2X:
> - encoder_pixel_multiplier = 2;
> - break;
> - case SDVO_CLOCK_RATE_MULT_4X:
> - encoder_pixel_multiplier = 4;
> - break;
> + if (intel_sdvo_get_value(intel_sdvo, SDVO_CMD_GET_CLOCK_RATE_MULT,
> + &val, 1)) {
> + switch (val) {
> + case SDVO_CLOCK_RATE_MULT_1X:
> + encoder_pixel_multiplier = 1;
> + break;
> + case SDVO_CLOCK_RATE_MULT_2X:
> + encoder_pixel_multiplier = 2;
> + break;
> + case SDVO_CLOCK_RATE_MULT_4X:
> + encoder_pixel_multiplier = 4;
> + break;
> + }
> }
>
> if(HAS_PCH_SPLIT(dev))
> --
> 1.8.3.1
>
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