Merge tag 'smp-urgent-2026-06-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull misc CPU hotplug fixes from Ingo Molnar:

 - Fix CPU hotplug error handling rollback bug (Bradley Morgan)

 - Fix possible output OOB write bug in the sysfs hotplug states
   printing code (Bradley Morgan)

* tag 'smp-urgent-2026-06-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  cpu: hotplug: Bound hotplug states sysfs output
  cpu: hotplug: Preserve per instance callback errors

1 files changed, 8 insertions, 12 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f975bb34915b..b3c8553d7bd6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -174,7 +174,7 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
 	struct cpuhp_step *step = cpuhp_get_step(state);
 	int (*cbm)(unsigned int cpu, struct hlist_node *node);
 	int (*cb)(unsigned int cpu);
-	int ret, cnt;
+	int ret, cnt, rollback_ret;
 
 	if (st->fail == state) {
 		st->fail = CPUHP_INVALID;
@@ -238,12 +238,12 @@ err:
 			break;
 
 		trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
-		ret = cbm(cpu, node);
-		trace_cpuhp_exit(cpu, st->state, state, ret);
+		rollback_ret = cbm(cpu, node);
+		trace_cpuhp_exit(cpu, st->state, state, rollback_ret);
 		/*
 		 * Rollback must not fail,
 		 */
-		WARN_ON_ONCE(ret);
+		WARN_ON_ONCE(rollback_ret);
 	}
 	return ret;
 }
@@ -2854,21 +2854,17 @@ static const struct attribute_group cpuhp_cpu_attr_group = {
 	.name = "hotplug",
 };
 
-static ssize_t states_show(struct device *dev,
-				 struct device_attribute *attr, char *buf)
+static ssize_t states_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
-	ssize_t cur, res = 0;
+	ssize_t res = 0;
 	int i;
 
 	mutex_lock(&cpuhp_state_mutex);
 	for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
 		struct cpuhp_step *sp = cpuhp_get_step(i);
 
-		if (sp->name) {
-			cur = sprintf(buf, "%3d: %s\n", i, sp->name);
-			buf += cur;
-			res += cur;
-		}
+		if (sp->name)
+			res += sysfs_emit_at(buf, res, "%3d: %s\n", i, sp->name);
 	}
 	mutex_unlock(&cpuhp_state_mutex);
 	return res;