From 22e9788899df87296f03af052e125f3aacd518ae Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 3 Nov 2020 12:39:01 +0100 Subject: [PATCH 224/323] ptrace: fix ptrace_unfreeze_traced() race with rt-lock Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.215-rt107.tar.xz The patch "ptrace: fix ptrace vs tasklist_lock race" changed ptrace_freeze_traced() to take task->saved_state into account, but ptrace_unfreeze_traced() has the same problem and needs a similar fix: it should check/update both ->state and ->saved_state. Reported-by: Luis Claudio R. Goncalves Fixes: "ptrace: fix ptrace vs tasklist_lock race" Signed-off-by: Oleg Nesterov Signed-off-by: Sebastian Andrzej Siewior Cc: stable-rt@vger.kernel.org --- kernel/ptrace.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 71acb6341e639..fb5d1a19507da 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -213,8 +213,8 @@ static bool ptrace_freeze_traced(struct task_struct *task) static void ptrace_unfreeze_traced(struct task_struct *task) { - if (task->state != __TASK_TRACED) - return; + unsigned long flags; + bool frozen = true; WARN_ON(!task->ptrace || task->parent != current); @@ -223,12 +223,19 @@ static void ptrace_unfreeze_traced(struct task_struct *task) * Recheck state under the lock to close this race. */ spin_lock_irq(&task->sighand->siglock); - if (task->state == __TASK_TRACED) { - if (__fatal_signal_pending(task)) - wake_up_state(task, __TASK_TRACED); - else - task->state = TASK_TRACED; - } + + raw_spin_lock_irqsave(&task->pi_lock, flags); + if (task->state == __TASK_TRACED) + task->state = TASK_TRACED; + else if (task->saved_state == __TASK_TRACED) + task->saved_state = TASK_TRACED; + else + frozen = false; + raw_spin_unlock_irqrestore(&task->pi_lock, flags); + + if (frozen && __fatal_signal_pending(task)) + wake_up_state(task, __TASK_TRACED); + spin_unlock_irq(&task->sighand->siglock); } -- 2.44.0