Subject: Re: zd1211rw (2.6.22 sparc64): unaligned access (do_rx)
From: Johannes Berg <johannes@sipsolutions.net>
To: David Miller <davem@davemloft.net>
Cc: shaddy_baddah@hotmail.com, linux-wireless@vger.kernel.org,
	netdev@vger.kernel.org, Jean Tourrilhes <jt@hpl.hp.com>
In-Reply-To: <20071120.043423.42170421.davem@davemloft.net> (sfid-20071120_123450_985935_82C552CF)
References: <4740DF47.4040206@hotmail.com>
	 <20071119.002755.77617097.davem@davemloft.net>
	 <20071120.043423.42170421.davem@davemloft.net>
	 (sfid-20071120_123450_985935_82C552CF)
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Date: Tue, 20 Nov 2007 14:15:40 +0100
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> I think I've figured out what's happening here.
>=20
> The kernel makes no effort whatsoever to translate iwe streams in
> compat environments.  And userspace then tries to "correct" this and
> does so miserably.  Likely this is what causes the bus error.

Quite possible. I wanted this fixed too but Jean refused to do it in the
kernel. And personally, I'm no longer touching wext with a 10 foot pole.
Too much backslash.

> The fix is that we need to add some handling code
> fs/compat_ioctl.c:do_wireless_ioctl() for the case where we are
> returning an iwe stream (SIOCGIWSCAN).
>=20
> It should not be very difficult to do this, since the compat format
> will be the same size or smaller, it should be easy to recode the
> thing in-place in the user buffer.
>=20
> So you make a pass over the user buffer fixing things up and then you
> adjust the iw_data length for the new size.
>=20
> Alternatively, you can allocate a kernel buffer for this, use a 'fs =3D
> get_fs(); set_fs(KERNEL_DS); ioctl(); set_fs(fs);' sequence, fixup the
> iwe stream, then copy the everything back out to userspace.

That may work, but wext also broadcasts iw_point inside netlink messages
for scan notifications etc. I don't see a good way to fix this part.

> Then we can delete all of this incredibly stupid code in the wireless
> tools that attempts to fix this up in userspace.

I wish. Really, I do.

johannes

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