Re: [PATCH][2/2] ide-tape: small cleanups - handle copy_to|from_user()failures

[Jesper Juhl]

On Sun, 28 Nov 2004, Jesper Juhl wrote:

> On Sun, 28 Nov 2004, Alan Cox wrote:
> 
> > On Sul, 2004-11-28 at 16:32, Jesper Juhl wrote:
> > >  #endif /* IDETAPE_DEBUG_BUGS */
> > >  		count = min((unsigned int)(bh->b_size - atomic_read(&bh->b_count)), (unsigned int)n);
> > > -		copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count);
> > > +		if (copy_from_user(bh->b_data + atomic_read(&bh->b_count), buf, count))
> > > +			return -EFAULT;
> > >  		n -= count;
> > >  		atomic_add(count, &bh->b_count);
> > >  		buf += count;
> > 
> > If you do this then you don't fix up tape->bh for further operations.
> 
> True, if copy_from_user fails it just bails out, I didn't see anything 
> really bad that could happen from that, but I'm an idiot, looking at it 
> again I guess it could probably mess up tape->bh pretty bad.
> Guess I need to go back and look at this in greater detail.

Does this really matter though?  if copy_from_user fails here the function 
bails out, and with the other changes I made the caller will bail out as 
well with the effect that the entire IO operation will fail. and once a 
new read or write is submitted we get a brand new tape->bh
Am I completely brain-dead or is it not in fact OK as I wrote it the first 
time?


-- 
Jesper Juhl

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