[PATCH 5.15.y] net: rfkill: prevent unlimited numbers of rfkill events from being created

[Sasha Levin <sashal@kernel.org>]

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

[ Upstream commit ea245d78dec594372e27d8c79616baf49e98a4a1 ]

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>
[ replaced `scoped_guard()` with explicit `mutex_lock()`/`mutex_unlock()` calls ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/rfkill/core.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/net/rfkill/core.c b/net/rfkill/core.c
index 068c7bcd30c94..7bcb7a9c1fcfd 100644
--- a/net/rfkill/core.c
+++ b/net/rfkill/core.c
@@ -72,11 +72,14 @@ 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;
 };
@@ -254,10 +257,12 @@ 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;
@@ -270,6 +275,16 @@ 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);
+
+	mutex_lock(&data->mtx);
+	if (data->event_count++ > MAX_RFKILL_EVENT) {
+		data->event_count--;
+		mutex_unlock(&data->mtx);
+		return -ENOSPC;
+	}
+	list_add_tail(&int_ev->list, &data->events);
+	mutex_unlock(&data->mtx);
+	return 0;
 }
 
 static void rfkill_send_events(struct rfkill *rfkill, enum rfkill_operation op)
@@ -281,10 +296,10 @@ static void rfkill_send_events(struct rfkill *rfkill, enum rfkill_operation op)
 		ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 		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);
 	}
 }
@@ -1149,7 +1164,6 @@ static int rfkill_fop_open(struct inode *inode, struct file *file)
 	init_waitqueue_head(&data->read_wait);
 
 	mutex_lock(&rfkill_global_mutex);
-	mutex_lock(&data->mtx);
 	/*
 	 * start getting events from elsewhere but hold mtx to get
 	 * startup events added first
@@ -1159,11 +1173,10 @@ static int rfkill_fop_open(struct inode *inode, struct file *file)
 		ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 		if (!ev)
 			goto free;
-		rfkill_fill_event(&ev->ev, rfkill, RFKILL_OP_ADD);
-		list_add_tail(&ev->list, &data->events);
+		if (rfkill_fill_event(ev, rfkill, data, RFKILL_OP_ADD))
+			kfree(ev);
 	}
 	list_add(&data->list, &rfkill_fds);
-	mutex_unlock(&data->mtx);
 	mutex_unlock(&rfkill_global_mutex);
 
 	file->private_data = data;
@@ -1171,7 +1184,6 @@ static int rfkill_fop_open(struct inode *inode, struct file *file)
 	return stream_open(inode, file);
 
  free:
-	mutex_unlock(&data->mtx);
 	mutex_unlock(&rfkill_global_mutex);
 	mutex_destroy(&data->mtx);
 	list_for_each_entry_safe(ev, tmp, &data->events, list)
@@ -1232,6 +1244,7 @@ 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);
-- 
2.53.0