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-rw-r--r--kernel/ptrace.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 227fec36b12a..9a34bd80a745 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -697,6 +697,8 @@ static int ptrace_peek_siginfo(struct task_struct *child,
static int ptrace_resume(struct task_struct *child, long request,
unsigned long data)
{
+ bool need_siglock;
+
if (!valid_signal(data))
return -EIO;
@@ -724,8 +726,26 @@ static int ptrace_resume(struct task_struct *child, long request,
user_disable_single_step(child);
}
+ /*
+ * Change ->exit_code and ->state under siglock to avoid the race
+ * with wait_task_stopped() in between; a non-zero ->exit_code will
+ * wrongly look like another report from tracee.
+ *
+ * Note that we need siglock even if ->exit_code == data and/or this
+ * status was not reported yet, the new status must not be cleared by
+ * wait_task_stopped() after resume.
+ *
+ * If data == 0 we do not care if wait_task_stopped() reports the old
+ * status and clears the code too; this can't race with the tracee, it
+ * takes siglock after resume.
+ */
+ need_siglock = data && !thread_group_empty(current);
+ if (need_siglock)
+ spin_lock_irq(&child->sighand->siglock);
child->exit_code = data;
wake_up_state(child, __TASK_TRACED);
+ if (need_siglock)
+ spin_unlock_irq(&child->sighand->siglock);
return 0;
}