vegam_smumgr.c: accessing mvdd_voltage_table.entries[] array out of bounds in function vegam_populate_smc_mvdd_table

Submitted by Robert Strube

Assigned to Default DRI bug account

Link to original bug (#108609)

Description

Created attachment 142298
Patch to fix accessing mvdd_voltage_table.entries[] array out of bounds in vegam_smumgr.c

I believe I've discovered a small bug in the vegam_smumgr.c, specifically the following function:

static int vegam_populate_smc_mvdd_table(struct pp_hwmgr *hwmgr,
SMU75_Discrete_DpmTable *table)
{
struct smu7_hwmgr data = (struct smu7_hwmgr )(hwmgr->backend);
uint32_t count, level;

if (SMU7_VOLTAGE_CONTROL_BY_GPIO == data->mvdd_control) {
count = data->mvdd_voltage_table.count;
if (count > SMU_MAX_SMIO_LEVELS)
count = SMU_MAX_SMIO_LEVELS;
for (level = 0; level < count; level++) {
table->SmioTable2.Pattern[level].Voltage = PP_HOST_TO_SMC_US(
data->mvdd_voltage_table.entries[count].value * VOLTAGE_SCALE);
/ Index into DpmTable.Smio. Drive bits from Smio entry to get this voltage level./
table->SmioTable2.Pattern[level].Smio =
(uint8_t) level;
table->Smio[level] |=
data->mvdd_voltage_table.entries[level].smio_low;
}
table->SmioMask2 = data->mvdd_voltage_table.mask_low;

table->MvddLevelCount = (uint32_t) PP_HOST_TO_SMC_UL(count);
}

return 0;
}

With the lines (within the for loop):

table->SmioTable2.Pattern[level].Voltage = PP_HOST_TO_SMC_US(
data->mvdd_voltage_table.entries[count].value * VOLTAGE_SCALE);

If this code was executed it would try to access the mvdd_voltage_table.entries[] array out of bounds, because count > than the max value for level.

I believe:

data->mvdd_voltage_table.entries[count].value

should actually be:

data->mvdd_voltage_table.entries[level].value

You can see in a similar function within vegam_smumgr.c, this bug is not present:

static int vegam_populate_smc_vddci_table(struct pp_hwmgr *hwmgr,
struct SMU75_Discrete_DpmTable *table)
{
uint32_t count, level;
struct smu7_hwmgr *data = (struct smu7_hwmgr *)(hwmgr->backend);

count = data->vddci_voltage_table.count;

if (SMU7_VOLTAGE_CONTROL_BY_GPIO == data->vddci_control) {
if (count > SMU_MAX_SMIO_LEVELS)
count = SMU_MAX_SMIO_LEVELS;
for (level = 0; level < count; ++level) {
table->SmioTable1.Pattern[level].Voltage = PP_HOST_TO_SMC_US(
data->vddci_voltage_table.entries[level].value * VOLTAGE_SCALE);
table->SmioTable1.Pattern[level].Smio = (uint8_t) level;

table->Smio[level] |= data->vddci_voltage_table.entries[level].smio_low;
}
}

table->SmioMask1 = data->vddci_voltage_table.mask_low;

return 0;
}

I've attached a patch for kernel 4.19, admittedly the change is trivial but I figured I would try to do things the right way :)

Thanks!
Rob

Patch 142298, "Patch to fix accessing mvdd_voltage_table.entries[] array out of bounds in vegam_smumgr.c":
vegam_smumgr.c.patch