netdev - Re: [PATCH] cmtp: fix argument error

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Date:   Mon, 3 Apr 2023 11:56:50 +0200
From:   Simon Horman <simon.horman@...igine.com>
To:     michenyuan <michenyuan@...wei.com>
Cc:     "isdn@...ux-pingi.de" <isdn@...ux-pingi.de>,
        "marcel@...tmann.org" <marcel@...tmann.org>,
        "johan.hedberg@...il.com" <johan.hedberg@...il.com>,
        "luiz.dentz@...il.com" <luiz.dentz@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cmtp: fix argument error

On Mon, Apr 03, 2023 at 02:35:21AM +0000, michenyuan wrote:
> Thank you for your suggestion.
> 
> This bug may not cause serious security problem. Function 'bt_sock_unregister' takes its parameter as an index and nulls the corresponding element of 'bt_proto' which is an array of pointers. When 'bt_proto' dereferences each element, it would check whether the element is empty or not. Therefore, the problem of null pointer deference does not occur.
> 
> This bug is observed by manually code review.

Thanks, could I suggest that you post a v2 that looks a bit like this:

Subject: Re: [PATCH v2 net-next] bluetooth: unregister correct BTPROTO for CMTP

On error unregister BTPROTO_CMTP to match the registration earlier
in the same code-path. Without this change BTPROTO_HIDP is incorrectly
unregistered.

This bug does not appear to cause serious security problem.

The function 'bt_sock_unregister' takes its parameter as an index and NULLs
the corresponding element of 'bt_proto' which is an array of pointers. When
'bt_proto' dereferences each element, it would check whether the element is
empty or not. Therefore, the problem of null pointer deference does not
occur.

Found by inspection.

Fixes: 8c8de589cedd ("Bluetooth: Added /proc/net/cmtp via bt_procfs_init()")
Signed-off-by: ...

...

> > ---
> >  net/bluetooth/cmtp/sock.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Code change looks good.
> 
> > diff --git a/net/bluetooth/cmtp/sock.c b/net/bluetooth/cmtp/sock.c 
> > index 96d49d9fae96..cf4370055ce2 100644
> > --- a/net/bluetooth/cmtp/sock.c
> > +++ b/net/bluetooth/cmtp/sock.c
> > @@ -250,7 +250,7 @@ int cmtp_init_sockets(void)
> >  	err = bt_procfs_init(&init_net, "cmtp", &cmtp_sk_list, NULL);
> >  	if (err < 0) {
> >  		BT_ERR("Failed to create CMTP proc file");
> > -		bt_sock_unregister(BTPROTO_HIDP);
> > +		bt_sock_unregister(BTPROTO_CMTP);
> >  		goto error;
> >  	}
> >  
> > --
> > 2.25.1