[PATCH] reject taskset for kernel threads

[Olaf Hering <olaf@aepfle.de>]

Do not allow taskset for kernel threads.
These commands will cause oopses due to stack corruption:

ls /proc/*/task | grep -v ^/ | xargs echo | xargs -n1 taskset -pc 2-9
taskset -pc 1 $$
taskset -pc 0 $((pidof john))

Possible fix in userland:

for i in ` ls /proc/*/task | grep -v ^/ `
do
	e=/proc/*/task/$i/exe
	if test -e $e
	then
		taskset -pc 2-9	$i
	fi
done


Signed-off-by: Olaf Hering <olaf@aepfle.de>

---
 kernel/sched.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-2.6.20/kernel/sched.c
===================================================================
--- linux-2.6.20.orig/kernel/sched.c
+++ linux-2.6.20/kernel/sched.c
@@ -4310,6 +4310,8 @@ long sched_setaffinity(pid_t pid, cpumas
 	read_unlock(&tasklist_lock);
 
 	retval = -EPERM;
+	if (!p->mm)
+		goto out_unlock;
 	if ((current->euid != p->euid) && (current->euid != p->uid) &&
 			!capable(CAP_SYS_NICE))
 		goto out_unlock;