[S] Change in coreboot[master]: nb/intel/gm45: Prevent null-deref in get_blc_pwm_freq_value()

[Jakub Czapiga (Code Review)]

Jakub Czapiga has submitted this change. ( https://review.coreboot.org/c/coreboot/+/74179 )

Change subject: nb/intel/gm45: Prevent null-deref in get_blc_pwm_freq_value()
......................................................................

nb/intel/gm45: Prevent null-deref in get_blc_pwm_freq_value()

IF its first call is get_blc_pwm_freq_value(NULL), null dereference
will occur.

Now when the parameter is NULL, it will return the value of the static
blc_pwm_freq directly, so the original behavior is kept.

Signed-off-by: Bill XIE 
Change-Id: I32354aa0fe1a3ca725c2031f973ffad0bda81ad5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74179
Tested-by: build bot (Jenkins) 
Reviewed-by: Arthur Heymans 
---
M src/northbridge/intel/gm45/gma.c
1 file changed, 21 insertions(+), 1 deletion(-)

Approvals:
  build bot (Jenkins): Verified
  Arthur Heymans: Looks good to me, approved

diff --git a/src/northbridge/intel/gm45/gma.c b/src/northbridge/intel/gm45/gma.c
index 7df9106..8043822 100644
--- a/src/northbridge/intel/gm45/gma.c
+++ b/src/northbridge/intel/gm45/gma.c
@@ -67,7 +67,8 @@
    int i;
    int blc_array_len;

-	if (blc_pwm_freq > 0)
+	/* Prevent null-deref on strcmp() below */
+	if (blc_pwm_freq > 0 || !edid_ascii_string)
    	return blc_pwm_freq;

blc_array_len = get_blc_values(&blc_pwm);