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memcg: fix possible panic when CONFIG_MM_OWNER=y

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When mm destruction happens, we should pass mm_update_next_owner() the old mm.
 But unfortunately new mm is passed in exec_mmap().

Thus, kernel panic is possible when a multi-threaded process uses exec().

Also, the owner member comment description is wrong.  mm->owner does not
necessarily point to the thread group leader.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: "Paul Menage" <menage@google.com>
Cc: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KOSAKI Motohiro 2008-05-12 14:02:31 -07:00 committed by Linus Torvalds
parent c9bfcb3151
commit 4cd1a8fc3d
2 changed files with 12 additions and 3 deletions
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2
fs/exec.c
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@ -736,7 +736,7 @@ static int exec_mmap(struct mm_struct *mm)
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);

13
include/linux/mm_types.h
View file

@ -226,8 +226,17 @@ 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