linux-kernel - Re: [050/107] block: check for proper length of iov entries earlier in blk_rq_map_user

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Message-ID: <20111104190616.GB3366@decadent.org.uk>
Date:	Fri, 4 Nov 2011 19:06:16 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg KH <gregkh@...e.de>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	Xiaotian Feng <dfeng@...hat.com>,
	Jens Axboe <jaxboe@...ionio.com>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk
Subject: Re: [050/107] block: check for proper length of iov entries
 earlier in blk_rq_map_user_iov()

On Fri, Nov 04, 2011 at 10:14:26AM -0700, Greg KH wrote:
> On Fri, Nov 04, 2011 at 03:24:16PM +0000, Ben Hutchings wrote:
> > On Wed, 2011-11-02 at 15:14 -0700, Greg KH wrote:
> > > 2.6.32-longterm review patch.  If anyone has any objections, please let us know.
> > > 
> > > ------------------
> > > 
> > > From: Xiaotian Feng <dfeng@...hat.com>
> > > 
> > > commit 5478755616ae2ef1ce144dded589b62b2a50d575 upstream.
> > > 
> > > commit 9284bcf checks for proper length of iov entries in
> > > blk_rq_map_user_iov(). But if the map is unaligned, kernel
> > > will break out the loop without checking for the proper length.
> > > So we need to check the proper length before the unalign check.
> > 
> > This will catch an unaligned zero-length entry.  But there's still no
> > check for zero-length iov entries *after* the unaligned entry.
> > 
> > [...]
> > > --- a/block/blk-map.c
> > > +++ b/block/blk-map.c
> > > @@ -201,12 +201,13 @@ int blk_rq_map_user_iov(struct request_q
> > >  	for (i = 0; i < iov_count; i++) {
> > >  		unsigned long uaddr = (unsigned long)iov[i].iov_base;
> > >  
> > > +		if (!iov[i].iov_len)
> > > +			return -EINVAL;
> > > +
> > >  		if (uaddr & queue_dma_alignment(q)) {
> > >  			unaligned = 1;
> > >  			break;
> > 
> > I think the correct fix is just to remove the 'break'.
> 
> Then the fix should go upstream first :)

But if I'm right, this is a non-fix and doesn't belong in the
longterm update.

Ben.

-- 
Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
                                                              - Albert Camus
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