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Date: Wed, 2 Sep 2020 20:31:25 +0800 From: Coiby Xu <coiby.xu@...il.com> To: Marcel Holtmann <marcel@...tmann.org> Cc: linux-bluetooth <linux-bluetooth@...r.kernel.org>, linux-kernel-mentees@...ts.linuxfoundation.org, Greg KH <gregkh@...uxfoundation.org>, syzkaller-bugs@...glegroups.com, syzbot+dd768a260f7358adbaf9@...kaller.appspotmail.com, Johan Hedberg <johan.hedberg@...il.com>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] Bluetooth: fix "list_add double add" in hci_conn_complete_evt On Mon, Aug 31, 2020 at 06:06:18PM +0200, Marcel Holtmann wrote: >Hi Coiby, Hi Marcel, Thank you for reviewing this patch! > >> When two HCI_EV_CONN_COMPLETE event packets with status=0 of the same >> HCI connection are received, device_add would be called twice which >> leads to kobject_add being called twice. Thus duplicate >> (struct hci_conn *conn)->dev.kobj.entry would be inserted into >> (struct hci_conn *conn)->dev.kobj.kset->list. >> >> This issue can be fixed by checking (struct hci_conn *conn)->debugfs. >> If it's not NULL, it means the HCI connection has been completed and we >> won't duplicate the work as for processing the first >> HCI_EV_CONN_COMPLETE event. > >do you have a btmon trace for this happening? Please see the attachment "btmon_output" which is a plain text file. I couldn't find a way to save traces in btsnoop format (the kernel would panic immediately after running the re-producer before QEMU has a chance to write the btsnoop file to the disk image). I've also also attached a simplified re-producer rep9_min.c if it interests you. > >> Reported-and-tested-by: syzbot+dd768a260f7358adbaf9@...kaller.appspotmail.com >> Link: https://syzkaller.appspot.com/bug?extid=dd768a260f7358adbaf9 >> Signed-off-by: Coiby Xu <coiby.xu@...il.com> >> --- >> net/bluetooth/hci_event.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c >> index 4b7fc430793c..1233739ce760 100644 >> --- a/net/bluetooth/hci_event.c >> +++ b/net/bluetooth/hci_event.c >> @@ -2605,6 +2605,11 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, struct sk_buff *skb) >> } >> >> if (!ev->status) { >> + if (conn->debugfs) { >> + bt_dev_err(hdev, "The connection has been completed"); >> + goto unlock; >> + } >> + > >And instead of doing papering over a hole, I would rather detect that the HCI event is not valid since we already received one for this connection. To check conn->debugfs is what I think could be used to detect this duplicate HCI event. Or you are suggesting this is not sufficient and implement something like a state machine instead? > >Regards > >Marcel > -- Best regards, Coiby View attachment "btmon_output" of type "text/plain" (14656 bytes) View attachment "rep9_min.c" of type "text/plain" (7471 bytes)
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