Re: [PATCH v3 0/2] usb: Check for DMA capable buffer sanity

From: Wolfram Sang <wsa@the-dreams.de>
To: Vignesh R <vigneshr@ti.com>
Cc: "Florian Fainelli" <f.fainelli@gmail.com>,
	linux-kernel@vger.kernel.org,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Felipe Balbi" <balbi@kernel.org>,
	"Peter Chen" <peter.chen@nxp.com>,
	"Roger Quadros" <rogerq@ti.com>,
	"Alan Stern" <stern@rowland.harvard.edu>,
	"Mathias Nyman" <mathias.nyman@linux.intel.com>,
	"Javier Martinez Canillas" <javier@osg.samsung.com>,
	"Baoyou Xie" <baoyou.xie@linaro.org>,
	"Sekhar Nori" <nsekhar@ti.com>,
	"William wu" <wulf@rock-chips.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Chris Bainbridge" <chris.bainbridge@gmail.com>,
	"Wolfram Sang" <wsa-dev@sang-engineering.com>,
	"Krzysztof Opasiak" <k.opasiak@samsung.com>,
	"Felix Hädicke" <felixhaedicke@web.de>,
	"Colin Ian King" <colin.king@canonical.com>,
	"open list:USB SUBSYSTEM" <linux-usb@vger.kernel.org>,
	clemens@ladisch.de, maksim.salau@gmail.com
Subject: Re: [PATCH v3 0/2] usb: Check for DMA capable buffer sanity
Date: Wed, 31 May 2017 17:12:37 +0200	[thread overview]
Message-ID: <20170531151237.GA2399@katana> (raw)
In-Reply-To: <dd2b5c78-4ed6-319a-9531-c0641af33a66@ti.com>

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> > +/* only works in process context because of stack detection */
> > +static inline bool is_dma_capable_addr(void *addr)
> > +{
> > +	return !(is_vmalloc_or_module_addr(addr) ||
> > +		 object_is_on_stack(addr));
> 
> This does not catch kmap'ed buffers which are not directly DMA'able.
> I would suggest to use virt_addr_valid() instead. Something like:
> 
> 	return (virt_addr_valid(addr) && !object_is_on_stack(addr));

Hehe, here is the part of the commit message I have for this code:

===

Second note: I am not even sure the checks complete (kmapped mem?). But
that just strengthens the argument of having on centralized place IMO :)

===

So, thanks for the heads up!

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