linux-kernel - Re: [PATCH] Bluetooth/l2cap: Fix uaf in l2cap

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Message-ID: <CABBYNZKg28ccCZXqBphNLp0WEOznS89Z-AiShC53JAVbsSsbGw@mail.gmail.com>
Date: Mon, 23 Sep 2024 11:48:04 -0400
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Aleksandr Nogikh <nogikh@...gle.com>
Cc: Hillf Danton <hdanton@...a.com>, Edward Adam Davis <eadavis@...com>, 
	syzbot+c12e2f941af1feb5632c@...kaller.appspotmail.com, 
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] Bluetooth/l2cap: Fix uaf in l2cap_connect

Hi,

On Mon, Sep 23, 2024 at 11:20 AM Luiz Augusto von Dentz
<luiz.dentz@...il.com> wrote:
>
> Hi Aleksandr,
>
> On Mon, Sep 23, 2024 at 10:37 AM Aleksandr Nogikh <nogikh@...gle.com> wrote:
> >
> > On Mon, Sep 23, 2024 at 4:33 PM Luiz Augusto von Dentz
> > <luiz.dentz@...il.com> wrote:
> > >
> > > Hi Hillf,
> > >
> > > On Sat, Sep 21, 2024 at 6:56 AM Hillf Danton <hdanton@...a.com> wrote:
> > > >
> > > > On Tue, Sep 10, 2024 at 4:56 PM Luiz Augusto von Dentz <luiz.dentz@...il.com> wrote:
> > > > >
> > > > > Maybe something like the following would be a better approach:
> > > > >
> > > > > https://gist.github.com/Vudentz/121a15fa4391b2b1f6c7e8d420a6846e
> > > >
> > > > If your idea is not bad, boy, feel free to win Tested-by from syzbot with it.
> > >
> > > Is there a way to quickly check a patch with syzbot?
> >
> > You can send a `#syz test` command in a reply to syzbot and attach the
> > patch-to-test to the email message.
> >
> > See https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches
>

Lets try again with git diff output:

#syz test

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index d6976db02c06..b2f8f9c5b610 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3782,6 +3782,8 @@ static void hci_acldata_packet(struct hci_dev
*hdev, struct sk_buff *skb)

     hci_dev_lock(hdev);
     conn = hci_conn_hash_lookup_handle(hdev, handle);
+    if (conn && hci_dev_test_flag(hdev, HCI_MGMT))
+        mgmt_device_connected(hdev, conn, NULL, 0);
     hci_dev_unlock(hdev);

     if (conn) {
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 1c82dcdf6e8f..b87c0f1dab9e 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3706,7 +3706,7 @@ static void hci_remote_features_evt(struct
hci_dev *hdev, void *data,
         goto unlock;
     }

-    if (!ev->status && !test_bit(HCI_CONN_MGMT_CONNECTED, &conn->flags)) {
+    if (!ev->status) {
         struct hci_cp_remote_name_req cp;
         memset(&cp, 0, sizeof(cp));
         bacpy(&cp.bdaddr, &conn->dst);
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 9988ba382b68..6544c1ed7143 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4066,17 +4066,9 @@ static void l2cap_connect(struct l2cap_conn
*conn, struct l2cap_cmd_hdr *cmd,
 static int l2cap_connect_req(struct l2cap_conn *conn,
                  struct l2cap_cmd_hdr *cmd, u16 cmd_len, u8 *data)
 {
-    struct hci_dev *hdev = conn->hcon->hdev;
-    struct hci_conn *hcon = conn->hcon;
-
     if (cmd_len < sizeof(struct l2cap_conn_req))
         return -EPROTO;

-    hci_dev_lock(hdev);
-    if (hci_dev_test_flag(hdev, HCI_MGMT))
-        mgmt_device_connected(hdev, hcon, NULL, 0);
-    hci_dev_unlock(hdev);
-
     l2cap_connect(conn, cmd, data, L2CAP_CONN_RSP);
     return 0;
 }