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authorKai Shen <shenkai8@huawei.com>2019-11-07 05:08:17 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-12-01 09:17:39 +0100
commit61e73cf57ed81f63ccce6209f16568578953a3ef (patch)
tree8ab3b2c38daace623a4a1bacea3ac227d5df01b4
parentf217cef919dacaab257df22355ae6d275c126f61 (diff)
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cpufreq: Add NULL checks to show() and store() methods of cpufreq
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>
-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 ace5ec65e36f..9d8d64f706e0 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -909,6 +909,9 @@ 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);
@@ -923,6 +926,9 @@ 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().