From 673db10729fb121ea1b16fe57791a0cb9eac1eb5 Mon Sep 17 00:00:00 2001 From: Bradley Morgan Date: Fri, 19 Jun 2026 16:37:17 +0000 Subject: [PATCH 1/2] cpu: hotplug: Preserve per instance callback errors cpuhp_invoke_callback() unwinds earlier callbacks for the same hotplug state when one instance fails. The rollback path currently reuses ret, so a successful rollback can hide the original error and make the failed transition look successful. Keep the rollback result separate from the original error. Fixes: 724a86881d03 ("smp/hotplug: Callback vs state-machine consistency") Signed-off-by: Bradley Morgan Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260619163719.12103-1-include@grrlz.net --- kernel/cpu.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 8df2d773fe3b..3ed24c711e3f 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -175,7 +175,7 @@ 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; @@ -239,12 +239,12 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, 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; } From 86f436567f2516a0083b210bedc933544826a2c3 Mon Sep 17 00:00:00 2001 From: Bradley Morgan Date: Fri, 19 Jun 2026 16:37:18 +0000 Subject: [PATCH 2/2] cpu: hotplug: Bound hotplug states sysfs output states_show() adds CPU hotplug state names into a single sysfs buffer using sprintf(). With enough registered states, this can write past the end of the PAGE_SIZE buffer. Use sysfs_emit_at() so output is bounded. Fixes: 98f8cdce1db5 ("cpu/hotplug: Add sysfs state interface") Signed-off-by: Bradley Morgan Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260619163719.12103-2-include@grrlz.net --- kernel/cpu.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 3ed24c711e3f..77fdb2013ab8 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2865,21 +2865,17 @@ 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;