From: Luiz Augusto von Dentz luiz.von.dentz@intel.com
[ Upstream commit b4f82f9ed43aefa79bec2504ae8c29be0c0f5d1d ]
After the hci sync command releases l2cap_conn, the hci receive data work queue references the released l2cap_conn when sending to the upper layer. Add hci dev lock to the hci receive data work queue to synchronize the two.
[1] BUG: KASAN: slab-use-after-free in l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954 Read of size 8 at addr ffff8880271a4000 by task kworker/u9:2/5837
CPU: 0 UID: 0 PID: 5837 Comm: kworker/u9:2 Not tainted 6.13.0-rc5-syzkaller-00163-gab75170520d4 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 Workqueue: hci1 hci_rx_work Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0x169/0x550 mm/kasan/report.c:489 kasan_report+0x143/0x180 mm/kasan/report.c:602 l2cap_build_cmd net/bluetooth/l2cap_core.c:2964 [inline] l2cap_send_cmd+0x187/0x8d0 net/bluetooth/l2cap_core.c:954 l2cap_sig_send_rej net/bluetooth/l2cap_core.c:5502 [inline] l2cap_sig_channel net/bluetooth/l2cap_core.c:5538 [inline] l2cap_recv_frame+0x221f/0x10db0 net/bluetooth/l2cap_core.c:6817 hci_acldata_packet net/bluetooth/hci_core.c:3797 [inline] hci_rx_work+0x508/0xdb0 net/bluetooth/hci_core.c:4040 process_one_work kernel/workqueue.c:3229 [inline] process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310 worker_thread+0x870/0xd30 kernel/workqueue.c:3391 kthread+0x2f0/0x390 kernel/kthread.c:389 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 </TASK>
Allocated by task 5837: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 poison_kmalloc_redzone mm/kasan/common.c:377 [inline] __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394 kasan_kmalloc include/linux/kasan.h:260 [inline] __kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4329 kmalloc_noprof include/linux/slab.h:901 [inline] kzalloc_noprof include/linux/slab.h:1037 [inline] l2cap_conn_add+0xa9/0x8e0 net/bluetooth/l2cap_core.c:6860 l2cap_connect_cfm+0x115/0x1090 net/bluetooth/l2cap_core.c:7239 hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline] hci_remote_features_evt+0x68e/0xac0 net/bluetooth/hci_event.c:3726 hci_event_func net/bluetooth/hci_event.c:7473 [inline] hci_event_packet+0xac2/0x1540 net/bluetooth/hci_event.c:7525 hci_rx_work+0x3f3/0xdb0 net/bluetooth/hci_core.c:4035 process_one_work kernel/workqueue.c:3229 [inline] process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310 worker_thread+0x870/0xd30 kernel/workqueue.c:3391 kthread+0x2f0/0x390 kernel/kthread.c:389 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Freed by task 54: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582 poison_slab_object mm/kasan/common.c:247 [inline] __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264 kasan_slab_free include/linux/kasan.h:233 [inline] slab_free_hook mm/slub.c:2353 [inline] slab_free mm/slub.c:4613 [inline] kfree+0x196/0x430 mm/slub.c:4761 l2cap_connect_cfm+0xcc/0x1090 net/bluetooth/l2cap_core.c:7235 hci_connect_cfm include/net/bluetooth/hci_core.h:2057 [inline] hci_conn_failed+0x287/0x400 net/bluetooth/hci_conn.c:1266 hci_abort_conn_sync+0x56c/0x11f0 net/bluetooth/hci_sync.c:5603 hci_cmd_sync_work+0x22b/0x400 net/bluetooth/hci_sync.c:332 process_one_work kernel/workqueue.c:3229 [inline] process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310 worker_thread+0x870/0xd30 kernel/workqueue.c:3391 kthread+0x2f0/0x390 kernel/kthread.c:389 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
Reported-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=31c2f641b850a348a734 Tested-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis eadavis@qq.com Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/bluetooth/l2cap_core.c | 39 +++++++++++++++++++++++++++++++++----- 1 file changed, 34 insertions(+), 5 deletions(-)
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 27b4c4a2ba1fd..adb8c33ac5953 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -948,6 +948,16 @@ static u8 l2cap_get_ident(struct l2cap_conn *conn) return id; }
+static void l2cap_send_acl(struct l2cap_conn *conn, struct sk_buff *skb, + u8 flags) +{ + /* Check if the hcon still valid before attempting to send */ + if (hci_conn_valid(conn->hcon->hdev, conn->hcon)) + hci_send_acl(conn->hchan, skb, flags); + else + kfree_skb(skb); +} + static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len, void *data) { @@ -970,7 +980,7 @@ static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len, bt_cb(skb)->force_active = BT_POWER_FORCE_ACTIVE_ON; skb->priority = HCI_PRIO_MAX;
- hci_send_acl(conn->hchan, skb, flags); + l2cap_send_acl(conn, skb, flags); }
static void l2cap_do_send(struct l2cap_chan *chan, struct sk_buff *skb) @@ -1792,13 +1802,10 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
mutex_unlock(&conn->chan_lock);
- hci_chan_del(conn->hchan); - if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT) cancel_delayed_work_sync(&conn->info_timer);
hcon->l2cap_data = NULL; - conn->hchan = NULL; l2cap_conn_put(conn); }
@@ -1806,6 +1813,7 @@ static void l2cap_conn_free(struct kref *ref) { struct l2cap_conn *conn = container_of(ref, struct l2cap_conn, ref);
+ hci_chan_del(conn->hchan); hci_conn_put(conn->hcon); kfree(conn); } @@ -7466,14 +7474,33 @@ static void l2cap_recv_reset(struct l2cap_conn *conn) conn->rx_len = 0; }
+static struct l2cap_conn *l2cap_conn_hold_unless_zero(struct l2cap_conn *c) +{ + BT_DBG("conn %p orig refcnt %u", c, kref_read(&c->ref)); + + if (!kref_get_unless_zero(&c->ref)) + return NULL; + + return c; +} + void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) { - struct l2cap_conn *conn = hcon->l2cap_data; + struct l2cap_conn *conn; int len;
+ /* Lock hdev to access l2cap_data to avoid race with l2cap_conn_del */ + hci_dev_lock(hcon->hdev); + + conn = hcon->l2cap_data; + if (!conn) conn = l2cap_conn_add(hcon);
+ conn = l2cap_conn_hold_unless_zero(conn); + + hci_dev_unlock(hcon->hdev); + if (!conn) goto drop;
@@ -7565,6 +7592,8 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) break; }
+ l2cap_conn_put(conn); + drop: kfree_skb(skb); }