Messages in this thread Patch in this message | | | Date | Thu, 08 May 2008 08:55:45 +0900 | From | KOSAKI Motohiro <> | Subject | [PATCH] on CONFIG_MM_OWNER=y, kernel panic is possible. take2 |
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> 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
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