linux-kernel - Re: [PATCH v2] i2c-hid: introduce HID over i2c specification implementation

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Message-ID: <alpine.LNX.2.00.1211091048590.27271@pobox.suse.cz>
Date:	Fri, 9 Nov 2012 10:49:21 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc:	Jiri Slaby <jslaby@...e.cz>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Stephane Chatty <chatty@...c.fr>, fabien.andre@...il.com,
	scott.liu@....com.tw, Jean Delvare <khali@...ux-fr.org>,
	JJ Ding <jj_ding@....com.tw>,
	Shubhrajyoti Datta <omaplinuxkernel@...il.com>,
	linux-i2c@...r.kernel.org, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] i2c-hid: introduce HID over i2c specification
 implementation

On Tue, 16 Oct 2012, Benjamin Tissoires wrote:

> >> --- /dev/null
> >> +++ b/drivers/hid/i2c-hid/i2c-hid.c
> > ...
> >> +static int i2c_hid_alloc_buffers(struct i2c_hid *ihid)
> >> +{
> >> +     /* the worst case is computed from the set_report command with a
> >> +      * reportID > 15 and the maximum report length */
> >> +     int args_len = sizeof(__u8) + /* optional ReportID byte */
> >> +                    sizeof(__u16) + /* data register */
> >> +                    sizeof(__u16) + /* size of the report */
> >> +                    ihid->bufsize; /* report */
> >> +
> >> +     ihid->inbuf = kzalloc(ihid->bufsize, GFP_KERNEL);
> >> +
> >> +     if (!ihid->inbuf)
> >> +             return -ENOMEM;
> >> +
> >> +     ihid->argsbuf = kzalloc(args_len, GFP_KERNEL);
> >> +
> >> +     if (!ihid->argsbuf) {
> >> +             kfree(ihid->inbuf);
> >> +             return -ENOMEM;
> >> +     }
> >> +
> >> +     ihid->cmdbuf = kzalloc(sizeof(union command) + args_len, GFP_KERNEL);
> >> +
> >> +     if (!ihid->cmdbuf) {
> >> +             kfree(ihid->inbuf);
> >> +             kfree(ihid->argsbuf);
> >> +             return -ENOMEM;
> >> +     }
> >> +
> >> +     return 0;
> >
> > If this is called from hid_start and some of the latter allocation fails
> > here, you free the buffers appropriately. However if another start
> > occurs (e.g. by loading another module for that particular device), it
> > will crash, as the buffers will remain unallocated because at this point
> > ihid->bufsize == old_bufsize. You should set ihid->bufsize back to
> > old_bufsize if i2c_hid_alloc_buffers fails and also set the pointers to
> > NULL here.
> 
> well spotted, thanks.
> I'll change it in v3 then.

Benjamin,

just a quick check -- are you planning on submitting v3 eventually?

Thanks,

-- 
Jiri Kosina
SUSE Labs
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