Messages in this thread Patch in this message | | | From | zanussi@kernel ... | Subject | [PATCH RT 2/3] ptrace: fix ptrace_unfreeze_traced() race with rt-lock | Date | Tue, 17 Nov 2020 11:19:47 -0600 |
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From: Oleg Nesterov <oleg@redhat.com>
v4.19.152-rt66-rc1 stable review patch. If anyone has any objections, please let me know.
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[ 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 a38b304fb9fd..cbefb0234be3 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -191,8 +191,8 @@ 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); @@ -201,12 +201,19 @@ 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); } -- 2.17.1
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