Merge tag 'tty-5.0-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

[linux.git] / kernel / fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index d439c48ecf181c5914cbf467a1754ac355c830f9..b69248e6f0e024c0407df16dfdc8a4919b590c78 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -164,10 +164,6 @@ static inline void free_task_struct(struct task_struct *tsk)
 }
 #endif
 
-void __weak arch_release_thread_stack(unsigned long *stack)
-{
-}
-
 #ifndef CONFIG_ARCH_THREAD_STACK_ALLOCATOR
 
 /*
@@ -221,6 +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;
        }
 
@@ -422,7 +419,6 @@ static void release_task_stack(struct task_struct *tsk)
                return;  /* Better to leak the stack than to free prematurely */
 
        account_kernel_stack(tsk, -1);
-       arch_release_thread_stack(tsk->stack);
        free_thread_stack(tsk);
        tsk->stack = NULL;
 #ifdef CONFIG_VMAP_STACK
@@ -1838,8 +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);
@@ -2005,6 +1999,17 @@ static __latent_entropy struct task_struct *copy_process(
        if (retval)
                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!