lkml.org 
[lkml]   [2009]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/2] task_struct cleanup: move binfmt field to mm_struct
(add Rusty)

On 07/27, Hiroshi Shimamoto wrote:
>
> void set_binfmt(struct linux_binfmt *new)
> {
> - if (current->binfmt)
> - module_put(current->binfmt->module);
> + struct mm_struct *mm = current->mm;
> +
> + BUG_ON(!mm);
> + if (mm->binfmt)

I am not sure we need this BUG_ON() above. If mm == NULL we will
have the same debug info after the crash.

> @@ -619,6 +621,9 @@ struct mm_struct *dup_mm(struct task_struct *tsk)
> mm->hiwater_rss = get_mm_rss(mm);
> mm->hiwater_vm = mm->total_vm;
>
> + if (mm->binfmt && !try_module_get(mm->binfmt->module))
> + goto free_pt;

free_pt does mmput() which calls module_put(mm->binfmt->module). This
is not right when try_module_get() fails. Hmm, the same if dup_mmap()
fails, we are doing an extra module_put().

Perhaps we can use __module_get() again, current->mm->binfmt holds a
reference. But this is a user-visible change, currently fork() can't
succeed if ->module->state == MODULE_STATE_GOING.

So I think we need another small change:

free_pt:
+ mm->binfmt = NULL;
mmput(mm);

Oleg.



\
 
 \ /
  Last update: 2009-07-27 19:05    [W:0.070 / U:4.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site