Merge tag 'v5.0-rc4' into asoc-5.1

Linux 5.0-rc4

1 files changed, 12 insertions, 2 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index a60459947f18..b69248e6f0e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -217,6 +217,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 		memset(s->addr, 0, THREAD_SIZE);
 
 		tsk->stack_vm_area = s;
+		tsk->stack = s->addr;
 		return s->addr;
 	}
 
@@ -1833,8 +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);
@@ -2001,6 +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!
 	 */