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(syn-107-146-107-067.res.spectrum.com. [107.146.107.67]) by smtp.gmail.com with ESMTPSA id ada2fe7eead31-4b68a33f4dfsm573185137.29.2025.01.17.10.42.03 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jan 2025 10:42:03 -0800 (PST) From: Luiz Augusto von Dentz To: linux-bluetooth@vger.kernel.org Subject: [PATCH v4] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd Date: Fri, 17 Jan 2025 13:42:02 -0500 Message-ID: <20250117184202.3895460-1-luiz.dentz@gmail.com> X-Mailer: git-send-email 2.47.1 Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Luiz Augusto von Dentz 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: __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 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 Signed-off-by: Luiz Augusto von Dentz Reported-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com Tested-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com --- net/bluetooth/l2cap_core.c | 45 ++++++++++++++++++++++++++++++++++---- 1 file changed, 41 insertions(+), 4 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 27b4c4a2ba1f..cc730135e5d9 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -951,11 +951,18 @@ static u8 l2cap_get_ident(struct l2cap_conn *conn) static void l2cap_send_cmd(struct l2cap_conn *conn, u8 ident, u8 code, u16 len, void *data) { - struct sk_buff *skb = l2cap_build_cmd(conn, code, ident, len, data); + struct sk_buff *skb; u8 flags; + /* Check if hchan has been dropped since it means hci_chan_del has + * been called. + */ + if (!conn->hchan) + return; + BT_DBG("code 0x%2.2x", code); + skb = l2cap_build_cmd(conn, code, ident, len, data); if (!skb) return; @@ -1751,12 +1758,16 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err) { struct l2cap_conn *conn = hcon->l2cap_data; struct l2cap_chan *chan, *l; + struct hci_chan *hchan; if (!conn) return; BT_DBG("hcon %p conn %p, err %d", hcon, conn, err); + hchan = conn->hchan; + conn->hchan = NULL; + kfree_skb(conn->rx_skb); skb_queue_purge(&conn->pending_rx); @@ -1792,13 +1803,12 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err) mutex_unlock(&conn->chan_lock); - hci_chan_del(conn->hchan); + hci_chan_del(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); } @@ -6785,6 +6795,12 @@ static void l2cap_recv_frame(struct l2cap_conn *conn, struct sk_buff *skb) u16 cid, len; __le16 psm; + /* Check if hchan has been dropped then drop any packets as well */ + if (!conn->hchan) { + kfree_skb(skb); + return; + } + if (hcon->state != BT_CONNECTED) { BT_DBG("queueing pending rx skb"); skb_queue_tail(&conn->pending_rx, skb); @@ -7466,14 +7482,33 @@ 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 +7600,8 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) break; } + l2cap_conn_put(conn); + drop: kfree_skb(skb); }