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Message-ID: <678fe297.050a0220.15cac.00b2.GAE@google.com>
Date: Tue, 21 Jan 2025 10:08:23 -0800
From: syzbot <syzbot+31c2f641b850a348a734@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] Re: [PATCH v4] Bluetooth: L2CAP: Fix slab-use-after-free
Read in l2cap_send_cmd
For archival purposes, forwarding an incoming command email to
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com.
***
Subject: Re: [PATCH v4] Bluetooth: L2CAP: Fix slab-use-after-free Read in l2cap_send_cmd
Author: luiz.dentz@...il.com
#syz test
On Fri, Jan 17, 2025 at 3:48 PM Luiz Augusto von Dentz
<luiz.dentz@...il.com> wrote:
>
> #syz test
>
> On Fri, Jan 17, 2025 at 1:42 PM Luiz Augusto von Dentz
> <luiz.dentz@...il.com> wrote:
> >
> > From: Luiz Augusto von Dentz <luiz.von.dentz@...el.com>
> >
> > 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@...kaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=31c2f641b850a348a734
> > Tested-by: syzbot+31c2f641b850a348a734@...kaller.appspotmail.com
> > Signed-off-by: Edward Adam Davis <eadavis@...com>
> > Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@...el.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);
> > }
> > --
> > 2.47.1
> >
>
>
> --
> Luiz Augusto von Dentz
--
Luiz Augusto von Dentz
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