linux-kernel - Re: [PATCH] bluetooth/rfcomm: fix ODEBUG bug in rfcomm_dev

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Message-Id: <449B4F83-8BCD-413C-823B-C7A5554801FB@holtmann.org>
Date:   Sun, 8 Mar 2020 09:18:39 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Qiujun Huang <hqjagain@...il.com>
Cc:     Johan Hedberg <johan.hedberg@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Bluez mailing list <linux-bluetooth@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bluetooth/rfcomm: fix ODEBUG bug in rfcomm_dev_ioctl

Hi Qiujun,

> Needn't call 'rfcomm_dlc_put' here, because 'rfcomm_dlc_exists' didn't
> increase dlc->refcnt.
> 
> Reported-by: syzbot+4496e82090657320efc6@...kaller.appspotmail.com
> Signed-off-by: Qiujun Huang <hqjagain@...il.com>
> ---
> net/bluetooth/rfcomm/tty.c | 1 -
> 1 file changed, 1 deletion(-)
> 
> diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
> index 0c7d31c..ea2a1df0 100644
> --- a/net/bluetooth/rfcomm/tty.c
> +++ b/net/bluetooth/rfcomm/tty.c
> @@ -414,7 +414,6 @@ static int __rfcomm_create_dev(struct sock *sk, void __user *arg)
> 		if (IS_ERR(dlc))
> 			return PTR_ERR(dlc);
> 		else if (dlc) {
> -			rfcomm_dlc_put(dlc);
> 			return -EBUSY;
> 		}
> 		dlc = rfcomm_dlc_alloc(GFP_KERNEL);

Please see the proposed change from Hillf.

It is better to not bother with the else if here since the if statement will already leave the function.

	if (dlc)
		return -EBUSY;

Regards

Marcel