[PATCH 16/18] x86_energy_perf_policy: Fix use-after-free in err_on_hypervisor()

[Len Brown <lenb@kernel.org>]

From: Len Brown <len.brown@intel.com>

Avoid testing a pointer into a freed buffer.

Assisted-by: GitHub-Copilot:Claude-Sonnet-4.6
Signed-off-by: Len Brown <len.brown@intel.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c  | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
index 70d889c3e0dc..f8ab9f4465ce 100644
--- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
+++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c
@@ -782,10 +782,10 @@ void err_on_hypervisor(void)
 	/* On VMs /proc/cpuinfo contains a "flags" entry for hypervisor */
 	cpuinfo = fopen_or_die("/proc/cpuinfo", "r");
 
-	buffer = malloc(4096);
+	buffer = calloc(4096, 1);
 	if (!buffer) {
 		fclose(cpuinfo);
-		err(-ENOMEM, "buffer malloc fail");
+		err(-ENOMEM, "buffer calloc fail");
 	}
 
 	if (!fread(buffer, 1024, 1, cpuinfo)) {
@@ -814,11 +814,10 @@ void err_on_hypervisor(void)
 	fclose(cpuinfo);
 
 	hypervisor = strstr(buffer, "hypervisor");
-
-	free(buffer);
-
 	if (hypervisor)
 		err(-1, "not supported on this virtual machine");
+
+	free(buffer);
 }
 
 /*
-- 
2.45.2