linux-kernel - [PATCH 1/3] tools/power turbostat: avoid segfault referencing fd_instr_count

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Message-ID: <20251118155813.533424-2-darcari@redhat.com>
Date: Tue, 18 Nov 2025 10:58:11 -0500
From: David Arcari <darcari@...hat.com>
To: lenb@...nel.org
Cc: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	David Arcari <darcari@...hat.com>
Subject: [PATCH 1/3] tools/power turbostat: avoid segfault referencing fd_instr_count_percpu

The problem is that fd_instr_count_percpu is allocated based on
the value of has_aperf. If has_aperf=0 then fd_instr_count_percpu
remains NULL. However, get_instr_count_fd() is called from
turbostat_init() based on the value of has_aperf_access.

On some VM systems has_aperf can be 0, while has_aperf_access can be
1.  In order to resolve the issue simply check for to see if
fd_instr_count_percpu is NULL and return -1 if it is.  Accordingly,
the has_aperf_access check can be removed from turbostat_init.

Signed-off-by: David Arcari <darcari@...hat.com>
Cc: Len Brown <lenb@...nel.org>
Cc: linux-kernel@...r.kernel.org
---
 tools/power/x86/turbostat/turbostat.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index f2512d78bcbd..584b0f7f9067 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -2463,6 +2463,9 @@ static long open_perf_counter(int cpu, unsigned int type, unsigned int config, i
 
 int get_instr_count_fd(int cpu)
 {
+	if (!fd_instr_count_percpu)
+		return -1;
+
 	if (fd_instr_count_percpu[cpu])
 		return fd_instr_count_percpu[cpu];
 
@@ -10027,7 +10030,7 @@ void turbostat_init()
 	for_all_cpus(get_cpu_type, ODD_COUNTERS);
 	for_all_cpus(get_cpu_type, EVEN_COUNTERS);
 
-	if (BIC_IS_ENABLED(BIC_IPC) && has_aperf_access && get_instr_count_fd(base_cpu) != -1)
+	if (BIC_IS_ENABLED(BIC_IPC) && get_instr_count_fd(base_cpu) != -1)
 		BIC_PRESENT(BIC_IPC);
 
 	/*
-- 
2.51.0