[PATCH 5/5] c/r: use pids objects for the pgrp/old_pgdp of ttys

[Oren Laadan <orenl@xxxxxxxxxxxxxxx>]

Make tty_old_pgrp and tty_pgrp use the shared pid instead of saving
the actual pid number in {checkpoint,restore}_signal().

Signed-off-by: Oren Laadan <orenl@xxxxxxxxxxxxxxx>
---
 kernel/signal.c |   42 ++++++++++++++++++++++++++++++++----------
 1 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 3842f5d..5c174a9 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3218,25 +3218,34 @@ static int checkpoint_signal(struct ckpt_ctx *ctx, struct task_struct *t)
 
 	/* tty */
 	if (signal->leader) {
-		h->tty_old_pgrp = ckpt_pid_nr(ctx, signal->tty_old_pgrp);
+		h->tty_old_pgrp = ckpt_lookup_pid(ctx, signal->tty_old_pgrp);
 		tty = tty_kref_get(signal->tty);
 		if (tty) {
 			/* irq is already disabled */
 			spin_lock(&tty->ctrl_lock);
-			h->tty_pgrp = ckpt_pid_nr(ctx, tty->pgrp);
+			h->tty_pgrp = ckpt_lookup_pid(ctx, tty->pgrp);
 			spin_unlock(&tty->ctrl_lock);
-			tty_kref_put(tty);
 		}
 	}
 
 	unlock_task_sighand(t, &flags);
 
 	/*
+	 * tty_pgrp must be in our namespace, since we are the
+	 * session leader and could not have unshared pidns !
+	 */
+	if (tty && h->tty_pgrp == 0) {
+		ckpt_err(ctx, -EBUSY, "%(T)tty_pgrp outside namespace\n");
+		ret = -EBUSY;
+		goto out;
+	}
+
+	/*
 	 * If the session is in an ancestor namespace, skip this tty
 	 * and set tty_objref = 0. It will not be explicitly restored,
 	 * but rather inherited from parent pid-ns at restart time.
 	 */
-	if (tty && ckpt_pid_nr(ctx, tty->session) > 0) {
+	if (tty && ckpt_lookup_pid(ctx, tty->session) > 0) {
 		h->tty_objref = checkpoint_obj(ctx, tty, CKPT_OBJ_TTY);
 		if (h->tty_objref < 0)
 			ret = h->tty_objref;
@@ -3255,6 +3264,7 @@ static int checkpoint_signal(struct ckpt_ctx *ctx, struct task_struct *t)
 	list_splice(&shared_pending.list, &signal->shared_pending.list);
 	unlock_task_sighand(t, &flags);
  out:
+	tty_kref_put(tty);
 	ckpt_hdr_put(ctx, h);
 	return ret;
 }
@@ -3339,6 +3349,10 @@ static int restore_signal(struct ckpt_ctx *ctx)
 
 	/* tty - session */
 	if (h->tty_objref) {
+		/*
+		 * should only get here if we are session leader, but
+		 * we don't explicitly check: forced by calls below
+		 */
 		tty = ckpt_obj_fetch(ctx, h->tty_objref, CKPT_OBJ_TTY);
 		if (IS_ERR(tty)) {
 			ret = PTR_ERR(tty);
@@ -3354,6 +3368,11 @@ static int restore_signal(struct ckpt_ctx *ctx)
 			 * If tty_pgrp == CKPT_PID_NULL, below will
 			 * fail, so no need for explicit test
 			 */
+			pgrp = ckpt_obj_fetch(ctx, h->tty_pgrp, CKPT_OBJ_PID);
+			if (IS_ERR(pgrp)) {
+				ret = PTR_ERR(pgrp);
+				goto out;
+			}
 			ret = do_tiocspgrp(tty, tty_pair_get_tty(tty),
 					   pid_vnr(pgrp));
 			if (ret < 0)
@@ -3382,13 +3401,16 @@ static int restore_signal(struct ckpt_ctx *ctx)
 	do_setitimer(ITIMER_VIRTUAL, &itimer, NULL);
 	do_setitimer(ITIMER_PROF, &itimer, NULL);
 
-	/* tty - tty_old_pgrp */
-	if (current->signal->leader && h->tty_old_pgrp != CKPT_PID_NULL) {
-		rcu_read_lock();
-		pgrp = get_pid(_ckpt_find_pgrp(ctx, h->tty_old_pgrp));
-		rcu_read_unlock();
-		if (!pgrp)
+	/*
+	 * tty - tty_old_pgrp: only for session leaders and for valid
+	 * tty_old_pgrp, ie, within our namespace, and not CKPT_PID_NULL.
+	 */
+	if (current->signal->leader && h->tty_old_pgrp > 0) {
+		pgrp = ckpt_obj_fetch(ctx, h->tty_old_pgrp, CKPT_OBJ_PID);
+		if (IS_ERR(pgrp)) {
+			ret = PTR_ERR(pgrp);
 			goto out;
+		}
 	}
 
 	spin_lock_irq(&current->sighand->siglock);
-- 
1.7.1

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