Merge tag 'gvt-fixes-2018-01-17' of https://github.com/intel/gvt-linux into drm-intel...

[uclinux-h8/linux.git] / kernel / fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index 5ad60d4..b69248e 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1834,8 +1834,6 @@ static __latent_entropy struct task_struct *copy_process(
 
        posix_cpu_timers_init(p);
 
-       p->start_time = ktime_get_ns();
-       p->real_start_time = ktime_get_boot_ns();
        p->io_context = NULL;
        audit_set_context(p, NULL);
        cgroup_fork(p);
@@ -2002,6 +2000,17 @@ static __latent_entropy struct task_struct *copy_process(
                goto bad_fork_free_pid;
 
        /*
+        * From this point on we must avoid any synchronous user-space
+        * communication until we take the tasklist-lock. In particular, we do
+        * not want user-space to be able to predict the process start-time by
+        * stalling fork(2) after we recorded the start_time but before it is
+        * visible to the system.
+        */
+
+       p->start_time = ktime_get_ns();
+       p->real_start_time = ktime_get_boot_ns();
+
+       /*
         * Make it visible to the rest of the system, but dont wake it up yet.
         * Need tasklist lock for parent etc handling!
         */