lkml.org 
[lkml]   [2019]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.4 112/132] cpufreq: Add NULL checks to show() and store() methods of cpufreq
Date
From: Kai Shen <shenkai8@huawei.com>

commit e6e8df07268c1f75dd9215536e2ce4587b70f977 upstream.

Add NULL checks to show() and store() in cpufreq.c to avoid attempts
to invoke a NULL callback.

Though some interfaces of cpufreq are set as read-only, users can
still get write permission using chmod which can lead to a kernel
crash, as follows:

chmod +w /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq

This bug was found in linux 4.19.

Signed-off-by: Kai Shen <shenkai8@huawei.com>
Reported-by: Feilong Lin <linfeilong@huawei.com>
Reviewed-by: Feilong Lin <linfeilong@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Subject & changelog ]
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/cpufreq/cpufreq.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -821,6 +821,9 @@ static ssize_t show(struct kobject *kobj
struct freq_attr *fattr = to_attr(attr);
ssize_t ret;

+ if (!fattr->show)
+ return -EIO;
+
down_read(&policy->rwsem);

if (fattr->show)
@@ -840,6 +843,9 @@ static ssize_t store(struct kobject *kob
struct freq_attr *fattr = to_attr(attr);
ssize_t ret = -EINVAL;

+ if (!fattr->store)
+ return -EIO;
+
get_online_cpus();

if (!cpu_online(policy->cpu))

\
 
 \ /
  Last update: 2019-11-27 21:38    [W:0.680 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site