[Lucid] [Patch 1/1] Fix ptrace when task is in task_is_stopped(), state
Colin Ian King
colin.king at canonical.com
Thu Mar 21 21:18:59 UTC 2013
On 21/03/13 20:57, John Johansen wrote:
> From d6a1da349c76ac2ebe4774d1da9fb7e660df01d3 Mon Sep 17 00:00:00 2001
> From: John Johansen <john.johansen at canonical.com>
> Date: Thu, 21 Mar 2013 05:04:13 -0700
> Subject: [PATCH] UBUNTU: SAUCE: Fix ptrace when task is in task_is_stopped()
> state
>
> This patch fixes a regression in ptrace, introduced by commit 9e74eb39
> (backport of 9899d11f) which makes assumptions about ptrace behavior
> which are not true in the 2.6.32 kernel.
>
> BugLink: http://bugs.launchpad.net/bugs/1145234
>
> 9899d11f makes the assumption that task_is_stopped() is not a valid state
> in ptrace because it is built on top of a series of patches which change
> how the TASK_STOPPED state is tracked (321fb561 which requires d79fdd6d
> and several other patches).
>
> Because Lucid does not have the set of patches that make task_is_stopped()
> an invalid state in ptrace_check_attach, partially revert 9e74eb39 so
> that ptrace_check_attach() correctly handles task_is_stopped(). However
> we must replace the assignment of TASK_TRACED with __TASK_TRACED to
> ensure TASK_WAKEKILL is cleared.
>
> Signed-off-by: John Johansen <john.johansen at canonical.com>
> ---
> kernel/ptrace.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index d0036f0..d9c8c47 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -81,14 +81,18 @@ void __ptrace_unlink(struct task_struct *child)
> }
>
> /* Ensure that nothing can wake it up, even SIGKILL */
> -static bool ptrace_freeze_traced(struct task_struct *task)
> +static bool ptrace_freeze_traced(struct task_struct *task, int kill)
> {
> - bool ret = false;
> + bool ret = true;
>
> spin_lock_irq(&task->sighand->siglock);
> - if (task_is_traced(task) && !__fatal_signal_pending(task)) {
> + if (task_is_stopped(task) && !__fatal_signal_pending(task))
> task->state = __TASK_TRACED;
> - ret = true;
> + else if (!kill) {
> + if (task_is_traced(task) && !__fatal_signal_pending(task))
> + task->state = __TASK_TRACED;
> + else
> + ret = false;
> }
> spin_unlock_irq(&task->sighand->siglock);
>
> @@ -131,7 +135,7 @@ int ptrace_check_attach(struct task_struct *child, int kill)
> * child->sighand can't be NULL, release_task()
> * does ptrace_unlink() before __exit_signal().
> */
> - if (kill || ptrace_freeze_traced(child))
> + if (ptrace_freeze_traced(child, kill))
> ret = 0;
> }
> read_unlock(&tasklist_lock);
>
I believe this fixes the original semantics as intended. I had to study
this a bit harder now that kill is passed into ptrace_freeze_traced()
but from what I can see this does the trick.
Acked-by: Colin Ian King <colin.king at canonical.com>
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