From 927cf4cc62bf7c41e5dbe74a111699819b79bcdf Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 3 Nov 2020 12:39:01 +0100 Subject: ptrace: fix ptrace_unfreeze_traced() race with rt-lock [ Upstream commit 0fdc91971b34cf6857b4cfd8c322ae936cfc189b ] 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 Signed-off-by: Tom Zanussi Signed-off-by: Luis Claudio R. Goncalves --- kernel/ptrace.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index cd869b487adc..c738827f29f7 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -203,8 +203,8 @@ 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); @@ -213,12 +213,19 @@ 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); } -- cgit v1.2.1