Merge tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull ptrace cleanups from Eric Biederman:
 "This set of changes removes tracehook.h, moves modification of all of
  the ptrace fields inside of siglock to remove races, adds a missing
  permission check to ptrace.c

  The removal of tracehook.h is quite significant as it has been a major
  source of confusion in recent years. Much of that confusion was around
  task_work and TIF_NOTIFY_SIGNAL (which I have now decoupled making the
  semantics clearer).

  For people who don't know tracehook.h is a vestiage of an attempt to
  implement uprobes like functionality that was never fully merged, and
  was later superseeded by uprobes when uprobes was merged. For many
  years now we have been removing what tracehook functionaly a little
  bit at a time. To the point where anything left in tracehook.h was
  some weird strange thing that was difficult to understand"

* tag 'ptrace-cleanups-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  ptrace: Remove duplicated include in ptrace.c
  ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE
  ptrace: Return the signal to continue with from ptrace_stop
  ptrace: Move setting/clearing ptrace_message into ptrace_stop
  tracehook: Remove tracehook.h
  resume_user_mode: Move to resume_user_mode.h
  resume_user_mode: Remove #ifdef TIF_NOTIFY_RESUME in set_notify_resume
  signal: Move set_notify_signal and clear_notify_signal into sched/signal.h
  task_work: Decouple TIF_NOTIFY_SIGNAL and task_work
  task_work: Call tracehook_notify_signal from get_signal on all architectures
  task_work: Introduce task_work_pending
  task_work: Remove unnecessary include from posix_timers.h
  ptrace: Remove tracehook_signal_handler
  ptrace: Remove arch_syscall_{enter,exit}_tracehook
  ptrace: Create ptrace_report_syscall_{entry,exit} in ptrace.h
  ptrace/arm: Rename tracehook_report_syscall report_syscall
  ptrace: Move ptrace_report_syscall into ptrace.h

1 files changed, 32 insertions, 30 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index e93de6daa188..368a34c25bbf 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -32,7 +32,7 @@
 #include <linux/signal.h>
 #include <linux/signalfd.h>
 #include <linux/ratelimit.h>
-#include <linux/tracehook.h>
+#include <linux/task_work.h>
 #include <linux/capability.h>
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
@@ -2229,14 +2229,17 @@ static void do_notify_parent_cldstop(struct task_struct *tsk,
  * That makes it a way to test a stopped process for
  * being ptrace-stopped vs being job-control-stopped.
  *
- * If we actually decide not to stop at all because the tracer
- * is gone, we keep current->exit_code unless clear_code.
+ * Returns the signal the ptracer requested the code resume
+ * with.  If the code did not stop because the tracer is gone,
+ * the stop signal remains unchanged unless clear_code.
  */
-static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t *info)
+static int ptrace_stop(int exit_code, int why, int clear_code,
+			unsigned long message, kernel_siginfo_t *info)
 	__releases(&current->sighand->siglock)
 	__acquires(&current->sighand->siglock)
 {
 	bool gstop_done = false;
+	bool read_code = true;
 
 	if (arch_ptrace_stop_needed()) {
 		/*
@@ -2278,6 +2281,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 	 */
 	smp_wmb();
 
+	current->ptrace_message = message;
 	current->last_siginfo = info;
 	current->exit_code = exit_code;
 
@@ -2344,8 +2348,9 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 
 		/* tasklist protects us from ptrace_freeze_traced() */
 		__set_current_state(TASK_RUNNING);
+		read_code = false;
 		if (clear_code)
-			current->exit_code = 0;
+			exit_code = 0;
 		read_unlock(&tasklist_lock);
 	}
 
@@ -2355,7 +2360,11 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 	 * any signal-sending on another CPU that wants to examine it.
 	 */
 	spin_lock_irq(&current->sighand->siglock);
+	if (read_code)
+		exit_code = current->exit_code;
 	current->last_siginfo = NULL;
+	current->ptrace_message = 0;
+	current->exit_code = 0;
 
 	/* LISTENING can be set only during STOP traps, clear it */
 	current->jobctl &= ~JOBCTL_LISTENING;
@@ -2366,9 +2375,10 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
 	 * This sets TIF_SIGPENDING, but never clears it.
 	 */
 	recalc_sigpending_tsk(current);
+	return exit_code;
 }
 
-static void ptrace_do_notify(int signr, int exit_code, int why)
+static int ptrace_do_notify(int signr, int exit_code, int why, unsigned long message)
 {
 	kernel_siginfo_t info;
 
@@ -2379,18 +2389,21 @@ static void ptrace_do_notify(int signr, int exit_code, int why)
 	info.si_uid = from_kuid_munged(current_user_ns(), current_uid());
 
 	/* Let the debugger run.  */
-	ptrace_stop(exit_code, why, 1, &info);
+	return ptrace_stop(exit_code, why, 1, message, &info);
 }
 
-void ptrace_notify(int exit_code)
+int ptrace_notify(int exit_code, unsigned long message)
 {
+	int signr;
+
 	BUG_ON((exit_code & (0x7f | ~0xffff)) != SIGTRAP);
-	if (unlikely(current->task_works))
+	if (unlikely(task_work_pending(current)))
 		task_work_run();
 
 	spin_lock_irq(&current->sighand->siglock);
-	ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED);
+	signr = ptrace_do_notify(SIGTRAP, exit_code, CLD_TRAPPED, message);
 	spin_unlock_irq(&current->sighand->siglock);
+	return signr;
 }
 
 /**
@@ -2545,11 +2558,10 @@ static void do_jobctl_trap(void)
 			signr = SIGTRAP;
 		WARN_ON_ONCE(!signr);
 		ptrace_do_notify(signr, signr | (PTRACE_EVENT_STOP << 8),
-				 CLD_STOPPED);
+				 CLD_STOPPED, 0);
 	} else {
 		WARN_ON_ONCE(!signr);
-		ptrace_stop(signr, CLD_STOPPED, 0, NULL);
-		current->exit_code = 0;
+		ptrace_stop(signr, CLD_STOPPED, 0, 0, NULL);
 	}
 }
 
@@ -2602,15 +2614,12 @@ static int ptrace_signal(int signr, kernel_siginfo_t *info, enum pid_type type)
 	 * comment in dequeue_signal().
 	 */
 	current->jobctl |= JOBCTL_STOP_DEQUEUED;
-	ptrace_stop(signr, CLD_TRAPPED, 0, info);
+	signr = ptrace_stop(signr, CLD_TRAPPED, 0, 0, info);
 
 	/* We're back.  Did the debugger cancel the sig?  */
-	signr = current->exit_code;
 	if (signr == 0)
 		return signr;
 
-	current->exit_code = 0;
-
 	/*
 	 * Update the siginfo structure if the signal has
 	 * changed.  If the debugger wanted something
@@ -2667,20 +2676,12 @@ bool get_signal(struct ksignal *ksig)
 	struct signal_struct *signal = current->signal;
 	int signr;
 
-	if (unlikely(current->task_works))
+	clear_notify_signal();
+	if (unlikely(task_work_pending(current)))
 		task_work_run();
 
-	/*
-	 * For non-generic architectures, check for TIF_NOTIFY_SIGNAL so
-	 * that the arch handlers don't all have to do it. If we get here
-	 * without TIF_SIGPENDING, just exit after running signal work.
-	 */
-	if (!IS_ENABLED(CONFIG_GENERIC_ENTRY)) {
-		if (test_thread_flag(TIF_NOTIFY_SIGNAL))
-			tracehook_notify_signal();
-		if (!task_sigpending(current))
-			return false;
-	}
+	if (!task_sigpending(current))
+		return false;
 
 	if (unlikely(uprobe_deny_signal()))
 		return false;
@@ -2939,7 +2940,8 @@ static void signal_delivered(struct ksignal *ksig, int stepping)
 	set_current_blocked(&blocked);
 	if (current->sas_ss_flags & SS_AUTODISARM)
 		sas_ss_reset(current);
-	tracehook_signal_handler(stepping);
+	if (stepping)
+		ptrace_notify(SIGTRAP, 0);
 }
 
 void signal_setup_done(int failed, struct ksignal *ksig, int stepping)