[tip: smp/urgent] cpu: hotplug: Bound hotplug states sysfs output

[tip-bot2 for Bradley Morgan]

The following commit has been merged into the smp/urgent branch of tip:

Commit-ID:     86f436567f2516a0083b210bedc933544826a2c3
Gitweb:        https://git.kernel.org/tip/86f436567f2516a0083b210bedc933544826a2c3
Author:        Bradley Morgan <include@xxxxxxxxx>
AuthorDate:    Fri, 19 Jun 2026 16:37:18 
Committer:     Thomas Gleixner <tglx@xxxxxxxxxx>
CommitterDate: Sun, 21 Jun 2026 20:44:00 +02:00

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 <include@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://patch.msgid.link/20260619163719.12103-2-include@xxxxxxxxx
---
 kernel/cpu.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 3ed24c7..77fdb20 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;