linux-kernel - [PATCH] tools/power x86_energy_perf_policy: Fix potential NULL pointer dereference

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Message-ID: <20251122151655.337040-1-mrout@redhat.com>
Date: Sat, 22 Nov 2025 20:46:52 +0530
From: Malaya Kumar Rout <mrout@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: mrout@...hat.com,
	malayarout91@...il.com,
	Len Brown <len.brown@...el.com>,
	Kaushlendra Kumar <kaushlendra.kumar@...el.com>
Subject: [PATCH] tools/power x86_energy_perf_policy: Fix potential NULL pointer dereference

In err_on_hypervisor(), strstr() is called to search for "flags" in the
buffer, but the return value is not checked before being used in pointer
arithmetic (flags - buffer). If strstr() returns NULL because "flags" is
not found in /proc/cpuinfo, this will cause undefined behavior and likely
a crash.

Add a NULL check after the strstr() call and handle the error appropriately
by cleaning up resources and reporting a meaningful error message.

Signed-off-by: Malaya Kumar Rout <mrout@...hat.com>
---
 .../x86/x86_energy_perf_policy/x86_energy_perf_policy.c      | 5 +++++
 1 file changed, 5 insertions(+)

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 884a4c746f32..be2a9c285a85 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
@@ -660,6 +660,11 @@ void err_on_hypervisor(void)
 	}
 
 	flags = strstr(buffer, "flags");
+	if (!flags) {
+		fclose(cpuinfo);
+		free(buffer);
+		err(1, "Failed to find 'flags' in /proc/cpuinfo");
+	}
 	rewind(cpuinfo);
 	fseek(cpuinfo, flags - buffer, SEEK_SET);
 	if (!fgets(buffer, 4096, cpuinfo)) {
-- 
2.51.0