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From a888cf3e5934c79d8edfca69dfe7fbe8f52c7476 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Tue, 3 Nov 2020 12:39:01 +0100
Subject: [PATCH 334/347] ptrace: fix ptrace_unfreeze_traced() race with
rt-lock
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz
[ 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 <lgoncalv@redhat.com>
Fixes: "ptrace: fix ptrace vs tasklist_lock race"
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
---
kernel/ptrace.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 9c59e523f3cd..b7d2a22534da 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -207,8 +207,8 @@ 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);
@@ -217,12 +217,19 @@ 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);
}
--
2.36.1
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