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Message-Id: <20221012081905.1800640-1-ajones@ventanamicro.com>
Date: Wed, 12 Oct 2022 10:19:05 +0200
From: Andrew Jones <ajones@...tanamicro.com>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Yury Norov <yury.norov@...il.com>
Subject: [PATCH v2] x86: Fix /proc/cpuinfo cpumask warning
Commit 78e5a3399421 ("cpumask: fix checking valid cpu range") has
started issuing warnings[*] when cpu indices equal to nr_cpu_ids - 1
are passed to cpumask_next* functions. seq_read_iter() and cpuinfo's
start and next seq operations implement a pattern like
n = cpumask_next(n - 1, mask);
show(n);
while (1) {
++n;
n = cpumask_next(n - 1, mask);
if (n >= nr_cpu_ids)
break;
show(n);
}
which will issue the warning when reading /proc/cpuinfo. Ensure no
warning is generated by validating the cpu index before calling
cpumask_next().
[*] Warnings will only appear with DEBUG_PER_CPU_MAPS enabled.
Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
Cc: Yury Norov <yury.norov@...il.com>
---
arch/x86/kernel/cpu/proc.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 099b6f0d96bd..94ac02c8dd6f 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -153,6 +153,9 @@ static int show_cpuinfo(struct seq_file *m, void *v)
static void *c_start(struct seq_file *m, loff_t *pos)
{
+ if (*pos >= nr_cpu_ids)
+ return NULL;
+
*pos = cpumask_next(*pos - 1, cpu_online_mask);
if ((*pos) < nr_cpu_ids)
return &cpu_data(*pos);
--
2.37.3
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