From: Oleg Nesterov <oleg@xxxxxxxxxx>
v4.19.152-rt66-rc1 stable review patch.
If anyone has any objections, please let me know.
-----------
[ 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@xxxxxxxxxx>
Fixes: "ptrace: fix ptrace vs tasklist_lock race"
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Tom Zanussi <zanussi@xxxxxxxxxx>
---
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
