Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
Your change looks correct to me. Thanks, Roland -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
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. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
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 21:41:02.0 +0300
> +++ PT/kernel/signal.c2007-11-22 16:59:35.0 +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);
> }
>
> /*
-
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[PATCH -mm 1/2] ptrace_stop: fix the race with ptrace detach+attach
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 <[EMAIL PROTECTED]>
--- PT/kernel/signal.c~1_ptrace_stop2007-11-21 21:41:02.0 +0300
+++ PT/kernel/signal.c 2007-11-22 16:59:35.0 +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);
}
/*
-
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