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authorKai Shen <shenkai8@huawei.com>2019-11-07 05:08:17 +0000
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2019-11-08 11:49:15 +0100
commite6e8df07268c1f75dd9215536e2ce4587b70f977 (patch)
treee175fbffe87247ea20ffee6fb4e32912f7d939ff /drivers/cpufreq
parent8d2eecead5bf23865cb73062a4e7139a9dbce5a1 (diff)
downloadlinux-e6e8df07268c1f75dd9215536e2ce4587b70f977.tar.bz2
cpufreq: Add NULL checks to show() and store() methods of cpufreq
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>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/cpufreq.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index dd1628192310..0a10cf9d0b1a 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -933,6 +933,9 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
struct freq_attr *fattr = to_attr(attr);
ssize_t ret;
+ if (!fattr->show)
+ return -EIO;
+
down_read(&policy->rwsem);
ret = fattr->show(policy, buf);
up_read(&policy->rwsem);
@@ -947,6 +950,9 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
struct freq_attr *fattr = to_attr(attr);
ssize_t ret = -EINVAL;
+ if (!fattr->store)
+ return -EIO;
+
/*
* cpus_read_trylock() is used here to work around a circular lock
* dependency problem with respect to the cpufreq_register_driver().