1 files changed, 43 insertions, 2 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 821cf1723814..2997ca600d18 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -31,6 +31,7 @@
 #include <linux/cn_proc.h>
 #include <linux/compat.h>
 #include <linux/sched/signal.h>
+#include <linux/minmax.h>
 
 #include <asm/syscall.h>	/* for syscall_get_* */
 
@@ -169,6 +170,21 @@ void __ptrace_unlink(struct task_struct *child)
 	spin_unlock(&child->sighand->siglock);
 }
 
+static bool looks_like_a_spurious_pid(struct task_struct *task)
+{
+	if (task->exit_code != ((PTRACE_EVENT_EXEC << 8) | SIGTRAP))
+		return false;
+
+	if (task_pid_vnr(task) == task->ptrace_message)
+		return false;
+	/*
+	 * The tracee changed its pid but the PTRACE_EVENT_EXEC event
+	 * was not wait()'ed, most probably debugger targets the old
+	 * leader which was destroyed in de_thread().
+	 */
+	return true;
+}
+
 /* Ensure that nothing can wake it up, even SIGKILL */
 static bool ptrace_freeze_traced(struct task_struct *task)
 {
@@ -179,7 +195,8 @@ static bool ptrace_freeze_traced(struct task_struct *task)
 		return ret;
 
 	spin_lock_irq(&task->sighand->siglock);
-	if (task_is_traced(task) && !__fatal_signal_pending(task)) {
+	if (task_is_traced(task) && !looks_like_a_spurious_pid(task) &&
+	    !__fatal_signal_pending(task)) {
 		task->state = __TASK_TRACED;
 		ret = true;
 	}
@@ -375,7 +392,7 @@ static int ptrace_attach(struct task_struct *task, long request,
 	audit_ptrace(task);
 
 	retval = -EPERM;
-	if (unlikely(task->flags & (PF_KTHREAD | PF_IO_WORKER)))
+	if (unlikely(task->flags & PF_KTHREAD))
 		goto out;
 	if (same_thread_group(task, current))
 		goto out;
@@ -779,6 +796,24 @@ static int ptrace_peek_siginfo(struct task_struct *child,
 	return ret;
 }
 
+#ifdef CONFIG_RSEQ
+static long ptrace_get_rseq_configuration(struct task_struct *task,
+					  unsigned long size, void __user *data)
+{
+	struct ptrace_rseq_configuration conf = {
+		.rseq_abi_pointer = (u64)(uintptr_t)task->rseq,
+		.rseq_abi_size = sizeof(*task->rseq),
+		.signature = task->rseq_sig,
+		.flags = 0,
+	};
+
+	size = min_t(unsigned long, size, sizeof(conf));
+	if (copy_to_user(data, &conf, size))
+		return -EFAULT;
+	return sizeof(conf);
+}
+#endif
+
 #ifdef PTRACE_SINGLESTEP
 #define is_singlestep(request)		((request) == PTRACE_SINGLESTEP)
 #else
@@ -1222,6 +1257,12 @@ int ptrace_request(struct task_struct *child, long request,
 		ret = seccomp_get_metadata(child, addr, datavp);
 		break;
 
+#ifdef CONFIG_RSEQ
+	case PTRACE_GET_RSEQ_CONFIGURATION:
+		ret = ptrace_get_rseq_configuration(child, addr, datavp);
+		break;
+#endif
+
 	default:
 		break;
 	}