net: rfkill: prevent unlimited numbers of rfkill events from being created

Userspace can create an unlimited number of rfkill events if the system
is so configured, while not consuming them from the rfkill file
descriptor, causing a potential out of memory situation.  Prevent this
from bounding the number of pending rfkill events at a "large" number
(i.e. 1000) to prevent abuses like this.

Cc: Johannes Berg <johannes@sipsolutions.net>
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/2026033013-disfigure-scroll-e25e@gregkh
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 24 insertions, 11 deletions

diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index 2444237bc36a..4827e1fb8804 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -73,11 +73,14 @@ struct rfkill_int_event {
 	struct rfkill_event_ext	ev;
 };
 
+/* Max rfkill events that can be "in-flight" for one data source */
+#define MAX_RFKILL_EVENT	1000
 struct rfkill_data {
 	struct list_head	list;
 	struct list_head	events;
 	struct mutex		mtx;
 	wait_queue_head_t	read_wait;
+	u32			event_count;
 	bool			input_handler;
 	u8			max_size;
 };
@@ -255,10 +258,12 @@ static void rfkill_global_led_trigger_unregister(void)
 }
 #endif /* CONFIG_RFKILL_LEDS */
 
-static void rfkill_fill_event(struct rfkill_event_ext *ev,
-			      struct rfkill *rfkill,
-			      enum rfkill_operation op)
+static int rfkill_fill_event(struct rfkill_int_event *int_ev,
+			     struct rfkill *rfkill,
+			     struct rfkill_data *data,
+			     enum rfkill_operation op)
 {
+	struct rfkill_event_ext *ev = &int_ev->ev;
 	unsigned long flags;
 
 	ev->idx = rfkill->idx;
@@ -271,6 +276,15 @@ static void rfkill_fill_event(struct rfkill_event_ext *ev,
 					RFKILL_BLOCK_SW_PREV));
 	ev->hard_block_reasons = rfkill->hard_block_reasons;
 	spin_unlock_irqrestore(&rfkill->lock, flags);
+
+	scoped_guard(mutex, &data->mtx) {
+		if (data->event_count++ > MAX_RFKILL_EVENT) {
+			data->event_count--;
+			return -ENOSPC;
+		}
+		list_add_tail(&int_ev->list, &data->events);
+	}
+	return 0;
 }
 
 static void rfkill_send_events(struct rfkill *rfkill, enum rfkill_operation op)
@@ -282,10 +296,10 @@ static void rfkill_send_events(struct rfkill *rfkill, enum rfkill_operation op)
 		ev = kzalloc_obj(*ev);
 		if (!ev)
 			continue;
-		rfkill_fill_event(&ev->ev, rfkill, op);
-		mutex_lock(&data->mtx);
-		list_add_tail(&ev->list, &data->events);
-		mutex_unlock(&data->mtx);
+		if (rfkill_fill_event(ev, rfkill, data, op)) {
+			kfree(ev);
+			continue;
+		}
 		wake_up_interruptible(&data->read_wait);
 	}
 }
@@ -1186,10 +1200,8 @@ static int rfkill_fop_open(struct inode *inode, struct file *file)
 		if (!ev)
 			goto free;
 		rfkill_sync(rfkill);
-		rfkill_fill_event(&ev->ev, rfkill, RFKILL_OP_ADD);
-		mutex_lock(&data->mtx);
-		list_add_tail(&ev->list, &data->events);
-		mutex_unlock(&data->mtx);
+		if (rfkill_fill_event(ev, rfkill, data, RFKILL_OP_ADD))
+			kfree(ev);
 	}
 	list_add(&data->list, &rfkill_fds);
 	mutex_unlock(&rfkill_global_mutex);
@@ -1259,6 +1271,7 @@ static ssize_t rfkill_fop_read(struct file *file, char __user *buf,
 		ret = -EFAULT;
 
 	list_del(&ev->list);
+	data->event_count--;
 	kfree(ev);
  out:
 	mutex_unlock(&data->mtx);