According to Documentation/ABI/testing/sysfs-devices-online, in order to control CPU N's hotplug state, we should write one of 'Yy1Nn0' to the file /sys/devices/system/cpu/cpuN/online, other values should be invalid. so the buffer length should be 2, buf[0] is one of 'Yy1Nn0' and buf[1] is '\n'.
without patch: [root@localhost home]# echo 0test > /sys/devices/system/cpu/cpu1/online [root@localhost home]# cat /sys/devices/system/cpu/cpu1/online 0 [root@localhost home]# echo 1test > /sys/devices/system/cpu/cpu1/online [root@localhost home]# cat /sys/devices/system/cpu/cpu1/online 1 [root@localhost home]# echo ntest > /sys/devices/system/cpu/cpu1/online [root@localhost home]# cat /sys/devices/system/cpu/cpu1/online 0 [root@localhost home]# echo ytest > /sys/devices/system/cpu/cpu1/online [root@localhost home]# cat /sys/devices/system/cpu/cpu1/online 1 [root@localhost home]# echo Ntest > /sys/devices/system/cpu/cpu1/online [root@localhost home]# cat /sys/devices/system/cpu/cpu1/online 0 [root@localhost home]# echo Ytest > /sys/devices/system/cpu/cpu1/online [root@localhost home]# cat /sys/devices/system/cpu/cpu1/online 1 with patch: [root@localhost home]# echo 0test > /sys/devices/system/cpu/cpu1/online bash: echo: write error: Invalid argument [root@localhost home]# echo 1test > /sys/devices/system/cpu/cpu1/online bash: echo: write error: Invalid argument [root@localhost home]# echo ntest > /sys/devices/system/cpu/cpu1/online bash: echo: write error: Invalid argument [root@localhost home]# echo ytest > /sys/devices/system/cpu/cpu1/online bash: echo: write error: Invalid argument [root@localhost home]# echo Ntest > /sys/devices/system/cpu/cpu1/online bash: echo: write error: Invalid argument [root@localhost home]# echo Ytest > /sys/devices/system/cpu/cpu1/online bash: echo: write error: Invalid argument Signed-off-by: Tiezhu Yang <kernelpa...@126.com> --- drivers/base/core.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/base/core.c b/drivers/base/core.c index 755451f..6588ed5 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -1005,6 +1005,12 @@ static ssize_t online_store(struct device *dev, struct device_attribute *attr, bool val; int ret; + /* According to Documentation/ABI/testing/sysfs-devices-online, + * the buf length should be 2, buf[0]: one of 'Yy1Nn0', buf[1]: '\n'. + */ + if (strlen(buf) != 2) + return -EINVAL; + ret = strtobool(buf, &val); if (ret < 0) return ret; -- 1.8.3.1