lkml.org 
[lkml]   [2002]   [Sep]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH] Fix for ptrace breakage
From
Date
Daniel Jacobowitz <dan@debian.org> writes:

> On Mon, Sep 16, 2002 at 09:44:34PM +0900, OGAWA Hirofumi wrote:
> > OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> writes:
> >
> > > Grr, sorry. This patch is bad version.
> > >
> > > list_for_each(_p, &father->ptrace_children) {
> > >
> > > of course, this should
> > >
> > > list_for_each_safe(_p, _n, &father->ptrace_children) {
> >
> > This is a patch which fixed the above. Please apply.
>
> Some comments. First of all, you said you fixed a race on
> current->ptrace and some other bugs - would you mind saying where they
> were? It's definitely cleaner after your patch but I'd like to
> understand where you found bugs, since I think you're introducing more.

It's the following

task_t *trace_task = p->parent;
int ptrace_flag = p->ptrace;
BUG_ON (ptrace_flag == 0);

__ptrace_unlink(p);
p->ptrace = ptrace_flag;
__ptrace_link(p, trace_task);

> If this is unnecessary, perhaps a BUG_ON()? This function is called
> from daemonize at which point the ptrace flag should be clear, and
> that's it.

You aren't looking the source.

void reparent_to_init(void)
{
write_lock_irq(&tasklist_lock);

ptrace_unlink(current);
/* Reparent to init */
REMOVE_LINKS(current);
current->parent = child_reaper;
current->real_parent = child_reaper;
SET_LINKS(current);

/* Set the exit signal to SIGCHLD so we signal init on exit */
current->exit_signal = SIGCHLD;

current->ptrace = 0;

> > @@ -443,7 +442,7 @@ void exit_mm(struct task_struct *tsk)
> > static inline void forget_original_parent(struct task_struct * father)
> > {
> > struct task_struct *p, *reaper = father;
> > - struct list_head *_p;
> > + struct list_head *_p, *_n;
> >
> > reaper = father->group_leader;
> > if (reaper == father)
> > @@ -462,52 +461,37 @@ static inline void forget_original_paren
> > if (father == p->real_parent)
> > reparent_thread(p, reaper, child_reaper);
> > }
> > - list_for_each(_p, &father->ptrace_children) {
> > + list_for_each_safe(_p, _n, &father->ptrace_children) {
> > p = list_entry(_p,struct task_struct,ptrace_list);
> > + list_del_init(&p->ptrace_list);
> > reparent_thread(p, reaper, child_reaper);
> > + if (p->parent != p->real_parent)
> > + list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
> > }
> > }
>
> So you reparent children on the ptrace_list right here. But they still
> need to go through zap_thread! You're right, the do_notify_parent in
> zap_thread isn't necessary; it'll be taken care of in sys_wait4. The
> orphaned pgrp check is still relevant though.

??? You forget tasklist_lock?

> If you're going to remove the if, you need to maintain its effect!
> See:
> > - if (p->parent != father) {
> > - BUG_ON(p->parent != p->real_parent);
> > - return;
> > - }
>
> This is the case where we were tracing something. The ptrace_unlink
> returned it to its original parent. It doesn't need the
> remove_parent/add_parent (though they are harmless); it does need to
> avoid the orphaned pgrp check. It may need the do_notify_parent check,
> which was a bug in the previous code.

What is the basis which you think it is bug?
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:28    [W:0.099 / U:1.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site