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From: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To: Larry Finger <Larry.Finger@lwfinger.net>,
	Phillip Potter <phil@philpotter.co.uk>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org,
	Pavel Skripkin <paskripkin@gmail.com>
Subject: Re: [PATCH 1/2] staging: r8188eu: Use usb_control_msg_recv/send() in usbctrl_vendorreq()
Date: Tue, 24 Aug 2021 14:01:02 +0200	[thread overview]
Message-ID: <6601006.JhxPbakEoc@localhost.localdomain> (raw)
In-Reply-To: <d5ac7cd8-dc81-732d-b583-628cd2a273cb@gmail.com>

On Tuesday, August 24, 2021 1:07:46 PM CEST Pavel Skripkin wrote:
> 
> Btw, not related to your patch, but I start think, that this check:
> 
> 
> 	if (!pIo_buf) {
> 		DBG_88E("[%s] pIo_buf == NULL\n", __func__);
> 		status = -ENOMEM;
> 		goto release_mutex;
> 	}
> 
> Should be wrapped as
> 
> 	if (WARN_ON(unlikely(!pIo_buf)) {
> 		...
> 	}
> 
> Since usb_vendor_req_buf is initialized in ->probe() and I can't see 
> possible calltrace, which can cause zeroing this pointer.

I see that usb_vendor_req_buf is initialized in rtw_init_intf_priv(). It depends on a 
kzalloc() success on allocating memory. Obviously it could fail to allocate. If it fails,
rtw_init_intf_priv() returns _FAIL to its caller(s) (whichever they are - I didn't go too 
deep in understanding the possible calls chains).

What does really matter is that dvobjpriv->usb_vendor_req_buf _could_ _indeed_ _be_
in an _un-initialized_ _status_ when it is assigned to pIo_buf.  

> Something _completely_ wrong is going on if usb_vendor_req_buf is NULL, 
> and we should complain loud about it. What do you think?

That "if (!pIo_buf)" in usbctrl_vendorreq() manages a possible but remote (I guess)
un-initialization by releasing a mutex and returning -ENOMEM.

I think that technically speaking it would suffice if callers read and manage properly 
the -ENOMEM returned by usbctrl_vendorreq(). 

Said that, I have no sufficient experience to say if exiting and returning -ENOMEM would
suffice to not make happen "_something _completely_ wrong_" or if a WARN_ON is required.
I'm sorry for not being able to go beyond the confirmation that indeed dvobjpriv->usb_vendor_req
could be un-initialized.

Regards,

Fabio

> With regards,
> Pavel Skripkin
> 





  reply	other threads:[~2021-08-24 12:01 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-23 22:37 [PATCH 0/2] staging: r8188eu: Use new usb_control_msg_recv/send() Fabio M. De Francesco
2021-08-23 22:37 ` [PATCH 1/2] staging: r8188eu: Use usb_control_msg_recv/send() in usbctrl_vendorreq() Fabio M. De Francesco
2021-08-24  0:08   ` Phillip Potter
2021-08-24  0:31     ` Fabio M. De Francesco
2021-08-24  1:38       ` Fabio M. De Francesco
2021-08-24  2:01         ` Fabio M. De Francesco
2021-08-24  5:44           ` Christophe JAILLET
2021-08-24 10:38             ` Fabio M. De Francesco
2021-08-24 17:03               ` Christophe JAILLET
2021-08-24 21:59         ` Phillip Potter
2021-08-24  8:13   ` Pavel Skripkin
2021-08-24  8:53     ` Fabio M. De Francesco
2021-08-24 11:07       ` Pavel Skripkin
2021-08-24 12:01         ` Fabio M. De Francesco [this message]
2021-08-24 12:09           ` Pavel Skripkin
2021-08-24 14:55             ` Fabio M. De Francesco
2021-08-23 22:37 ` [PATCH 2/2] staging: r8188eu: Make some clean-ups " Fabio M. De Francesco
2021-08-24  0:10   ` Phillip Potter

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