* [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
@ 2007-11-22 16:14 Oleg Nesterov
2007-11-23 10:23 ` Alexey Dobriyan
2007-12-11 1:36 ` Roland McGrath
0 siblings, 2 replies; 4+ messages in thread
From: Oleg Nesterov @ 2007-11-22 16:14 UTC (permalink / raw)
To: Andrew Morton
Cc: Alexey Dobriyan, Linus Torvalds, Roland McGrath,
Scott James Remnant, linux-kernel
If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops tasklist
and then changes the ->state from TASK_TRACED to TASK_RUNNING.
This can fool another tracer which attaches to us in between. Change the ->state
under tasklist_lock to ensure that ptrace_check_attach() can't wrongly succeed.
Also, remove the unnecessary mb().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
--- PT/kernel/signal.c~1_ptrace_stop 2007-11-21 21:41:02.000000000 +0300
+++ PT/kernel/signal.c 2007-11-22 16:59:35.000000000 +0300
@@ -1628,11 +1628,11 @@ static void ptrace_stop(int exit_code, i
} else {
/*
* By the time we got the lock, our tracer went away.
- * Don't stop here.
+ * Don't drop the lock yet, another tracer may come.
*/
- read_unlock(&tasklist_lock);
- set_current_state(TASK_RUNNING);
+ __set_current_state(TASK_RUNNING);
current->exit_code = nostop_code;
+ read_unlock(&tasklist_lock);
}
/*
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
2007-11-22 16:14 [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach Oleg Nesterov
@ 2007-11-23 10:23 ` Alexey Dobriyan
2007-11-23 10:54 ` Oleg Nesterov
2007-12-11 1:36 ` Roland McGrath
1 sibling, 1 reply; 4+ messages in thread
From: Alexey Dobriyan @ 2007-11-23 10:23 UTC (permalink / raw)
To: Oleg Nesterov
Cc: Andrew Morton, Linus Torvalds, Roland McGrath,
Scott James Remnant, linux-kernel
On Thu, Nov 22, 2007 at 07:14:59PM +0300, Oleg Nesterov wrote:
> If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops tasklist
> and then changes the ->state from TASK_TRACED to TASK_RUNNING.
>
> This can fool another tracer which attaches to us in between. Change the ->state
> under tasklist_lock to ensure that ptrace_check_attach() can't wrongly succeed.
ptrace_check_attach? Both do read_lock -- can run in parallel, so how can it help?
> --- PT/kernel/signal.c~1_ptrace_stop 2007-11-21 21:41:02.000000000 +0300
> +++ PT/kernel/signal.c 2007-11-22 16:59:35.000000000 +0300
> @@ -1628,11 +1628,11 @@ static void ptrace_stop(int exit_code, i
> } else {
> /*
> * By the time we got the lock, our tracer went away.
> - * Don't stop here.
> + * Don't drop the lock yet, another tracer may come.
> */
> - read_unlock(&tasklist_lock);
> - set_current_state(TASK_RUNNING);
> + __set_current_state(TASK_RUNNING);
> current->exit_code = nostop_code;
> + read_unlock(&tasklist_lock);
> }
>
> /*
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
2007-11-23 10:23 ` Alexey Dobriyan
@ 2007-11-23 10:54 ` Oleg Nesterov
0 siblings, 0 replies; 4+ messages in thread
From: Oleg Nesterov @ 2007-11-23 10:54 UTC (permalink / raw)
To: Alexey Dobriyan
Cc: Andrew Morton, Linus Torvalds, Roland McGrath,
Scott James Remnant, linux-kernel
On 11/23, Alexey Dobriyan wrote:
>
> On Thu, Nov 22, 2007 at 07:14:59PM +0300, Oleg Nesterov wrote:
> > If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops tasklist
> > and then changes the ->state from TASK_TRACED to TASK_RUNNING.
> >
> > This can fool another tracer which attaches to us in between. Change the ->state
> > under tasklist_lock to ensure that ptrace_check_attach() can't wrongly succeed.
>
> ptrace_check_attach? Both do read_lock -- can run in parallel,
Yep.
> so how can it help?
read_lock prevents ptrace_attach(), so the new tracer can't attach
and then do ptrace_check_attach().
Oleg.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
2007-11-22 16:14 [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach Oleg Nesterov
2007-11-23 10:23 ` Alexey Dobriyan
@ 2007-12-11 1:36 ` Roland McGrath
1 sibling, 0 replies; 4+ messages in thread
From: Roland McGrath @ 2007-12-11 1:36 UTC (permalink / raw)
To: Oleg Nesterov
Cc: Andrew Morton, Alexey Dobriyan, Linus Torvalds,
Scott James Remnant, linux-kernel
Your change looks correct to me.
Thanks,
Roland
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2007-12-11 1:36 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2007-11-22 16:14 [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach Oleg Nesterov
2007-11-23 10:23 ` Alexey Dobriyan
2007-11-23 10:54 ` Oleg Nesterov
2007-12-11 1:36 ` Roland McGrath
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