From ebe6674292fda9a58e6f3adffd6d277560857169 Mon Sep 17 00:00:00 2001 From: Chengfeng Ye Date: Sat, 22 Aug 2026 23:06:19 +0800 Subject: [PATCH] Bluetooth: RFCOMM: serialize session teardown rfcomm_kill_listener() walks session_list and deletes every session without holding rfcomm_mutex, unlike the normal session processing and connect error paths. Under normal operation, an open RFCOMM socket pins rfcomm.ko, so rfcomm_kill_listener() does not run concurrently with rfcomm_dlc_open(). However, forced module unload via delete_module(O_TRUNC) can stop krfcommd while a failed connect is still unwinding. connect task forced unload / krfcommd ------------ ------------------------ rfcomm_lock() rfcomm_session_add() delete_module("rfcomm", O_TRUNC) rfcomm_kill_listener() fetch session from session_list kernel_connect() fails rfcomm_session_del() remove and free session rfcomm_session_del(session) The final call then reads the freed session and may corrupt the list. KASAN reported with mdelay() to enlarge critical window: BUG: KASAN: slab-use-after-free in rfcomm_run+0x3802/0x3f00 [rfcomm] Read of size 8 at addr ffff888111058d40 by task krfcommd/79 Tainted: [R]=FORCED_RMMOD Allocated by task 86: rfcomm_session_add+0xa1/0x300 [rfcomm] rfcomm_dlc_open+0x8b2/0xf30 [rfcomm] rfcomm_sock_connect+0x34c/0x530 [rfcomm] Freed by task 86: kfree+0x121/0x3c0 rfcomm_dlc_open+0xab7/0xf30 [rfcomm] rfcomm_sock_connect+0x34c/0x530 [rfcomm] Hold rfcomm_mutex across the teardown traversal so every reachable session_list walk uses the same serialization. Reviewed-by: Ali Ahmet Memis Tested-by: Ali Ahmet Memis Reviewed-by: Pauli Virtanen Signed-off-by: Chengfeng Ye Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/rfcomm/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c index 63fa0f542ccf..f7463f092283 100644 --- a/net/bluetooth/rfcomm/core.c +++ b/net/bluetooth/rfcomm/core.c @@ -2182,8 +2182,10 @@ static void rfcomm_kill_listener(void) BT_DBG(""); + rfcomm_lock(); list_for_each_entry_safe(s, n, &session_list, list) rfcomm_session_del(s); + rfcomm_unlock(); } static int rfcomm_run(void *unused)