linux-kernel - Re: [PATCH 2/2] staging: et131x: Fix 64bit tx dma address handling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20121018101741.GA4503@mark-lap>
Date:	Thu, 18 Oct 2012 11:17:52 +0100
From:	Mark Einon <mark.einon@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jeffrey Ladouceur <jladouceur@...il.com>
Cc:	devel@...verdev.osuosl.org, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] staging: et131x: Fix 64bit tx dma address handling

On Thu, Oct 18, 2012 at 10:59:56AM +0100, Alan Cox wrote:
> > > +                                                         skb_headlen(skb),
> > > +                                                         DMA_TO_DEVICE);
> > > +                               desc[frag].addr_lo = dma_addr & 0xFFFFFFFF;
> > > +                               desc[frag].addr_hi = dma_addr >> 32;
> > 
> > Maybe use macros defined in kernel.h instead:
> > 
> > desc[frag].addr_lo = lower_32_bits(dma_addr);
> > desc[frag].addr_hi = upper_32_bits(dma_addr);
> > 
> > A few more instances below.
> 
> This is actually important because >> 32 of a 32bit value is undefined in
> C. The compiler is free to do what it likes with this. While the results
> are usually sane some architectures do generate the equivalent of
> 
> 		x >> (n % wordsize);
> 
> Alan

Thanks for the comments both. I'll send an updated patch this evening.

The intention is to eventually store this value as a dma_addr_t anyway,
but some more work needs to be done to copy the address correctly to the
desc ring.

Cheers,

Mark
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/