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fix stack out-of-bounds read in core cluster heuristic #429

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fix stack out-of-bounds read in core cluster heuristic #429

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30 changes: 30 additions & 0 deletions src/arm/linux/clusters.c
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Original file line number Diff line number Diff line change
Expand Up @@ -70,19 +70,23 @@ bool cpuinfo_arm_linux_detect_core_clusters_by_heuristic(
uint32_t max_processors,
struct cpuinfo_arm_linux_processor processors[restrict static max_processors]) {
uint32_t cluster_processors[3];
uint32_t expected_clusters;
switch (usable_processors) {
case 10:
cluster_processors[0] = 4;
cluster_processors[1] = 4;
cluster_processors[2] = 2;
expected_clusters = 3;
break;
case 8:
cluster_processors[0] = 4;
cluster_processors[1] = 4;
expected_clusters = 2;
break;
case 6:
cluster_processors[0] = 4;
cluster_processors[1] = 2;
expected_clusters = 2;
break;
#if defined(__ANDROID__) && CPUINFO_ARCH_ARM
case 5:
Expand All @@ -93,6 +97,7 @@ bool cpuinfo_arm_linux_detect_core_clusters_by_heuristic(
*/
cluster_processors[0] = 4;
cluster_processors[1] = 1;
expected_clusters = 2;
break;
#endif
default:
Expand All @@ -116,6 +121,28 @@ bool cpuinfo_arm_linux_detect_core_clusters_by_heuristic(
/* Expect this processor to start a new cluster
*/

if (cluster == expected_clusters) {
/*
* More processors carry the VALID flag
* than the usable_processors this
* heuristic was tabulated for, so the
* cluster table is exhausted. Happens
* when a processor is in the possible
* and present lists but missing from
* /proc/cpuinfo.
*/
cpuinfo_log_debug(
"heuristic detection of core clusters failed: "
"processor %" PRIu32 " would start cluster #%" PRIu32
", but only %" PRIu32 " clusters are expected for %" PRIu32
" usable processors",
i,
cluster,
expected_clusters,
usable_processors);
return false;
}

expected_cluster_exists = !!(processors[i].flags & CPUINFO_LINUX_FLAG_PACKAGE_CLUSTER);
if (expected_cluster_exists) {
if (processors[i].package_leader_id != i) {
Expand Down Expand Up @@ -350,6 +377,9 @@ bool cpuinfo_arm_linux_detect_core_clusters_by_heuristic(
*/

cluster_start = i;
/* This pass walks the same processors in the
* same order as the verification pass above, so
* cluster stays below expected_clusters. */
expected_cluster_processors = cluster_processors[cluster++];
} else {
/* Expect this processor to belong to the same
Expand Down