Messages in this thread | | | Date | Thu, 08 May 2008 19:23:41 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH] on CONFIG_MM_OWNER=y, kernel panic is possible. take2 |
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KOSAKI Motohiro wrote: >> I'd word it as >> >> /* >> * "owner" points to a task that is regarded as the canonical >> * user/owner of this mm. All of the following must be true in >> * order for it to be changed: >> * >> * current == mm->owner >> * current->mm != mm >> * new_owner->mm == mm >> * new_owner->alloc_lock is held >> */ > > Wow, Thank you a lot! > new version attached. > > Cheers! > > > ----------------------------------------------------------- > When mm destruct happend, We should pass mm_update_next_owner() > old mm. > but unfortunately new mm is passed in exec_mmap(). > > thus, kernel panic is possible when multi thread process use exec(). > > > and, owner member comment description is wrong. > mm->owner don't not necessarily point to thread group leader. > > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > CC: Balbir Singh <balbir@linux.vnet.ibm.com> > CC: "Paul Menage" <menage@google.com> > CC: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com> > > --- > fs/exec.c | 2 +- > include/linux/mm_types.h | 13 +++++++++++-- > 2 files changed, 12 insertions(+), 3 deletions(-) > > 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); > Index: b/include/linux/mm_types.h > =================================================================== > --- a/include/linux/mm_types.h 2008-05-08 09:20:13.000000000 +0900 > +++ b/include/linux/mm_types.h 2008-05-08 09:22:13.000000000 +0900 > @@ -231,8 +231,17 @@ struct mm_struct { > rwlock_t ioctx_list_lock; /* aio lock */ > struct kioctx *ioctx_list; > #ifdef CONFIG_MM_OWNER > - struct task_struct *owner; /* The thread group leader that */ > - /* owns the mm_struct. */ > + /* > + * "owner" points to a task that is regarded as the canonical > + * user/owner of this mm. All of the following must be true in > + * order for it to be changed: > + * > + * current == mm->owner > + * current->mm != mm > + * new_owner->mm == mm > + * new_owner->alloc_lock is held > + */ > + struct task_struct *owner; > #endif > > #ifdef CONFIG_PROC_FS >
Looks good to me, but I've not tested it
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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