From mboxrd@z Thu Jan 1 00:00:00 1970 From: Srinivas Pandruvada Subject: [PATCH 1/2] cpufreq: acpi_cpufreq: prevent crash on reading freqdomain_cpus Date: Thu, 1 Oct 2015 15:23:01 -0700 Message-ID: <1443738182-4077-1-git-send-email-srinivas.pandruvada@linux.intel.com> Return-path: Received: from mga09.intel.com ([134.134.136.24]:51414 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751007AbbJAWX5 (ORCPT ); Thu, 1 Oct 2015 18:23:57 -0400 Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: rafael.j.wysocki@intel.com, viresh.kumar@linaro.org Cc: linux-pm@vger.kernel.org, Srinivas Pandruvada When freqdomain_cpus attribute is read from an offlined cpu, it will cause crash. This change prevents calling cpufreq_show_cpus when mask is NULL. Alternatively we can add this NULL check in cpufreq_show_cpus function. Crash info: [ 170.814949] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 170.814990] IP: [] _find_next_bit.part.0+0x10/0x70 [ 170.815021] PGD 227d30067 PUD 229e56067 PMD 0 [ 170.815043] Oops: 0000 [#2] SMP [ 170.816022] CPU: 3 PID: 3121 Comm: cat Tainted: G D OE 4.3.0-rc3+ #33 ... ... [ 170.816657] Call Trace: [ 170.816672] [] ? find_next_bit+0x15/0x20 [ 170.816696] [] cpufreq_show_cpus+0x5c/0xd0 [ 170.816722] [] show_freqdomain_cpus+0x19/0x20 [acpi_cpufreq] [ 170.816749] [] show+0x3b/0x60 [ 170.816769] [] sysfs_kf_seq_show+0xbc/0x130 [ 170.816793] [] kernfs_seq_show+0x23/0x30 [ 170.816816] [] seq_read+0xec/0x390 [ 170.816837] [] kernfs_fop_read+0x10a/0x160 [ 170.816861] [] __vfs_read+0x37/0x100 [ 170.816883] [] ? security_file_permission+0xa0/0xc0 [ 170.816909] [] vfs_read+0x83/0x130 [ 170.816930] [] SyS_read+0x55/0xc0 ... ... [ 170.817185] ---[ end trace bc6eadf82b2b965a ]--- Signed-off-by: Srinivas Pandruvada --- drivers/cpufreq/acpi-cpufreq.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c index 7982772..cec1ee2 100644 --- a/drivers/cpufreq/acpi-cpufreq.c +++ b/drivers/cpufreq/acpi-cpufreq.c @@ -149,6 +149,9 @@ static ssize_t show_freqdomain_cpus(struct cpufreq_policy *policy, char *buf) { struct acpi_cpufreq_data *data = policy->driver_data; + if (unlikely(!data)) + return -ENODEV; + return cpufreq_show_cpus(data->freqdomain_cpus, buf); } -- 2.4.3