CPU online file permission

Is there a reason why the "online" file in the subdirectories for the CPUs
in /sys/devices/system isn't world-readable?  I cannot imagine it to be
security relevant especially now that a getcpu() syscall can be used to
determine what CPUa thread runs on.

The file is useful to correctly implement the sysconf() function to return
the number of online CPUs.  In the presence of hotplug we currently cannot
provide this information.  The patch below should to it.

Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index fe7ef33..4054507 100644 (file)
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -53,7 +53,7 @@ static ssize_t store_online(struct sys_device *dev, const char *buf,
                ret = count;
        return ret;
 }
-static SYSDEV_ATTR(online, 0600, show_online, store_online);
+static SYSDEV_ATTR(online, 0644, show_online, store_online);
 
 static void __devinit register_cpu_control(struct cpu *cpu)
 {