random: Mix cputime from each thread that exits to the pool

When a thread exits mix it's cputime (userspace + kernelspace) to the entropy pool. We don't know how "random" this is, so we use add_device_randomness that doesn't mess with entropy count. Signed-off-by: Nick Kossifidis <[email protected]> Signed-off-by: Theodore Ts'o <[email protected]>
kishon · Dec 17, 2012 · 6133705 · 6133705
1 parent ec8f02d
commit 6133705
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
@@ -9,6 +9,7 @@
 #include <asm/uaccess.h>
 #include <linux/kernel_stat.h>
 #include <trace/events/timer.h>
+#include <linux/random.h>
 
 /*
  * Called after updating RLIMIT_CPU to run cpu timer and update
@@ -494,6 +495,8 @@ static void cleanup_timers(struct list_head *head,
  */
 void posix_cpu_timers_exit(struct task_struct *tsk)
 {
+	add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
+						sizeof(unsigned long long));
 	cleanup_timers(tsk->cpu_timers,
 		       tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);