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

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Date:   Wed, 31 May 2017 17:12:37 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Vignesh R <vigneshr@...com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Peter Chen <peter.chen@....com>, Roger Quadros <rogerq@...com>,
        Alan Stern <stern@...land.harvard.edu>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Baoyou Xie <baoyou.xie@...aro.org>,
        Sekhar Nori <nsekhar@...com>, William wu <wulf@...k-chips.com>,
        Arnd Bergmann <arnd@...db.de>,
        Chris Bainbridge <chris.bainbridge@...il.com>,
        Wolfram Sang <wsa-dev@...g-engineering.com>,
        Krzysztof Opasiak <k.opasiak@...sung.com>,
        Felix Hädicke <felixhaedicke@....de>,
        Colin Ian King <colin.king@...onical.com>,
        "open list:USB SUBSYSTEM" <linux-usb@...r.kernel.org>,
        clemens@...isch.de, maksim.salau@...il.com
Subject: Re: [PATCH v3 0/2] usb: Check for DMA capable buffer sanity


> > +/* 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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