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

Damien Lespiau
2013-07-12T15:25:01Z

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>
---
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