linux-kernel - Re: [ 031/100] iwlwifi: always copy first 16 bytes of commands

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Date:	Thu, 14 Mar 2013 14:23:03 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	"Berg, Johannes" <johannes.berg@...el.com>
Cc:	"Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [ 031/100] iwlwifi: always copy first 16 bytes of commands

On Thu, 2013-03-14 at 06:31 +0000, Berg, Johannes wrote:
> > > >  	/* and copy the data that needs to be copied */
> > > >  	cmd_pos = offsetof(struct iwl_device_cmd, payload);
> > > > +	copy_size = sizeof(out_cmd->hdr);
> > > >  	for (i = 0; i < IWL_MAX_CMD_TFDS; i++) {
> > > > -		if (!cmd->len[i])
> > > > +		int copy = 0;
> > > > +
> > > > +		if (!cmd->len)
> > > >  			continue;
> > >
> > > cmd->len is an array, so the new condition is always false.  Shouldn't
> > > it be 'if (!cmdlen[i])'?
> > 
> > To answer myself: no, it should still be 'if (!cmd->len[i])' as this loop needs to
> > include input fragments that will be completely copied into the header
> > fragment.
> 
> Ick, good catch. It luckily doesn't matter as if cmd->len[i] is 0 (in
> which case we'd continue) the "if (copy)" below saves us in all the
> different code paths inside the loop. This is still clearly a mistake
> in the patch though.
> 
> I will fix this upstream, I guess you'll want to wait for that for
> stable? I'll Cc:stable that patch as well.

I agree with your analysis that this is actually harmless, so no
objections to including the patch in stable as it is.

Ben.

-- 
Ben Hutchings
Humans are not rational beings; they are rationalising beings.

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