4.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> commit e25303676e18a7947185a34e26dd08cf0c0ea573 upstream. When freqdomain_cpus attribute is read from an offlined cpu, it will cause crash. This change prevents calling cpufreq_show_cpus when policy driver_data is NULL. Crash info: [ 170.814949] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 170.814990] IP: [<ffffffff813b2490>] _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] [<ffffffff813b2505>] ? find_next_bit+0x15/0x20 [ 170.816696] [<ffffffff8160e47c>] cpufreq_show_cpus+0x5c/0xd0 [ 170.816722] [<ffffffffa031a409>] show_freqdomain_cpus+0x19/0x20 [acpi_cpufreq] [ 170.816749] [<ffffffff8160e65b>] show+0x3b/0x60 [ 170.816769] [<ffffffff8129b31c>] sysfs_kf_seq_show+0xbc/0x130 [ 170.816793] [<ffffffff81299be3>] kernfs_seq_show+0x23/0x30 [ 170.816816] [<ffffffff81240f2c>] seq_read+0xec/0x390 [ 170.816837] [<ffffffff8129a64a>] kernfs_fop_read+0x10a/0x160 [ 170.816861] [<ffffffff8121d9b7>] __vfs_read+0x37/0x100 [ 170.816883] [<ffffffff813217c0>] ? security_file_permission+0xa0/0xc0 [ 170.816909] [<ffffffff8121e2e3>] vfs_read+0x83/0x130 [ 170.816930] [<ffffffff8121f035>] SyS_read+0x55/0xc0 ... ... [ 170.817185] ---[ end trace bc6eadf82b2b965a ]--- Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/cpufreq/acpi-cpufreq.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/cpufreq/acpi-cpufreq.c +++ b/drivers/cpufreq/acpi-cpufreq.c @@ -146,6 +146,9 @@ static ssize_t show_freqdomain_cpus(stru { struct acpi_cpufreq_data *data = per_cpu(acfreq_data, policy->cpu); + if (unlikely(!data)) + return -ENODEV; + return cpufreq_show_cpus(data->freqdomain_cpus, buf); } -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html