Re: on CONFIG_MM_OWNER=y, kernel panic is possible.

[KOSAKI Motohiro]

> That is not possible. If you look at where mm_update_next_owner() is called
> from, we call it from
> 
> exit_mm() and exec_mmap()
> 
> In both cases, we ensure that the task's mm has changed (to NULL and the new mm
> respectively), before we call mm_update_next_owner(), hence c->mm can never be
> equal to p->mm.

if so, following patch is needed instead.



---
 fs/exec.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: b/fs/exec.c
===================================================================
--- a/fs/exec.c 2008-05-04 22:57:09.000000000 +0900
+++ b/fs/exec.c 2008-05-06 15:40:35.000000000 +0900
@@ -735,7 +735,7 @@ static int exec_mmap(struct mm_struct *m
        tsk->active_mm = mm;
        activate_mm(active_mm, mm);
        task_unlock(tsk);
-       mm_update_next_owner(mm);
+       mm_update_next_owner(old_mm);
        arch_pick_mmap_layout(mm);
        if (old_mm) {
                up_read(&old_mm->mmap_sem);


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