sched: Fix fork() error path to not crash

In dup_task_struct(), if arch_dup_task_struct() fails, the clean up
code fails to clean up correctly.  That's because the clean up
code depends on unininitalized ti->task pointer.  We fix this
by making sure that the task and thread_info know about each other
before we attempt to take the error path.

Signed-off-by: Salman Qazi <sqazi@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120626011815.11323.5533.stgit@dungbeetle.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index ab5211b9e622..f00e319d8376 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -304,12 +304,17 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
         }
 
         err = arch_dup_task_struct(tsk, orig);
-        if (err)
-                goto out;
 
+        /*
+         * We defer looking at err, because we will need this setup
+         * for the clean up path to work correctly.
+         */
         tsk->stack = ti;
-
         setup_thread_stack(tsk, orig);
+
+        if (err)
+                goto out;
+
         clear_user_return_notifier(tsk);
         clear_tsk_need_resched(tsk);
         stackend = end_of_stack(tsk);