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SMTP id e9e14a558f8ab-3cfafd2e8f0mr12267405ab.10.1737482903392; Tue, 21 Jan 2025 10:08:23 -0800 (PST) Date: Tue, 21 Jan 2025 10:08:23 -0800 In-Reply-To: <00000000000070784806124596ec@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <678fe297.050a0220.15cac.00b2.GAE@google.com> Subject: Re: [syzbot] Re: [PATCH v4] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: Re: [PATCH v4] Bluetooth: L2CAP: Fix slab-use-after-free Read in l= 2cap_send_cmd Author: luiz.dentz@gmail.com #syz test On Fri, Jan 17, 2025 at 3:48=E2=80=AFPM Luiz Augusto von Dentz wrote: > > #syz test > > On Fri, Jan 17, 2025 at 1:42=E2=80=AFPM Luiz Augusto von Dentz > wrote: > > > > From: Luiz Augusto von Dentz > > > > After the hci sync command releases l2cap_conn, the hci receive data wo= rk > > queue references the released l2cap_conn when sending to the upper laye= r. > > 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/bluet= ooth/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-syzka= ller-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=3D31c2f641b850a348a734 > > Tested-by: syzbot+31c2f641b850a348a734@syzkaller.appspotmail.com > > Signed-off-by: Edward Adam Davis > > Signed-off-by: Luiz Augusto von Dentz > > --- > > 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 =3D 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 =3D l2cap_build_cmd(conn, code, ident, len, data); > > if (!skb) > > return; > > > > @@ -1751,12 +1758,16 @@ static void l2cap_conn_del(struct hci_conn *hco= n, int err) > > { > > struct l2cap_conn *conn =3D 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 =3D conn->hchan; > > + conn->hchan =3D NULL; > > + > > kfree_skb(conn->rx_skb); > > > > skb_queue_purge(&conn->pending_rx); > > @@ -1792,13 +1803,12 @@ static void l2cap_conn_del(struct hci_conn *hco= n, 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 =3D NULL; > > - conn->hchan =3D 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 wel= l */ > > + if (!conn->hchan) { > > + kfree_skb(skb); > > + return; > > + } > > + > > if (hcon->state !=3D 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 =3D 0; > > } > > > > +static struct l2cap_conn *l2cap_conn_hold_unless_zero(struct l2cap_con= n *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, u1= 6 flags) > > { > > - struct l2cap_conn *conn =3D 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 =3D hcon->l2cap_data; > > + > > if (!conn) > > conn =3D l2cap_conn_add(hcon); > > > > + conn =3D 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, st= ruct sk_buff *skb, u16 flags) > > break; > > } > > > > + l2cap_conn_put(conn); > > + > > drop: > > kfree_skb(skb); > > } > > -- > > 2.47.1 > > > > > -- > Luiz Augusto von Dentz --=20 Luiz Augusto von Dentz