linux-kernel - Re: [dm-devel] [PATCH v3 01/26] block: Fix a buffer overrun in bio_integrity

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Message-ID: <20121002210143.GT26488@google.com>
Date:	Tue, 2 Oct 2012 14:01:43 -0700
From:	Kent Overstreet <koverstreet@...gle.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, axboe@...nel.dk,
	"Martin K. Petersen" <martin.petersen@...cle.com>, tj@...nel.org
Subject: Re: [dm-devel] [PATCH v3 01/26] block: Fix a buffer overrun in
 bio_integrity_split()

On Tue, Oct 02, 2012 at 04:32:53PM -0400, Vivek Goyal wrote:
> On Tue, Oct 02, 2012 at 01:26:43PM -0700, Kent Overstreet wrote:
> > On Tue, Oct 02, 2012 at 10:08:47AM -0400, Vivek Goyal wrote:
> > > On Mon, Oct 01, 2012 at 02:42:41PM -0700, Kent Overstreet wrote:
> > > 
> > > [..]
> > > > Here's the new patch:
> > > > 
> > > > 
> > > > commit e270c9ca843b5c86d59431b0d7a676b7846946d6
> > > > Author: Kent Overstreet <koverstreet@...gle.com>
> > > > Date:   Mon Oct 1 14:41:08 2012 -0700
> > > > 
> > > >     block: Fix a buffer overrun in bio_integrity_split()
> > > >     
> > > >     bio_integrity_split() seemed to be confusing pointers and arrays -
> > > >     bip_vec in bio_integrity_payload is an array appended to the end of the
> > > >     payload, so the bio_vecs in struct bio_pair need to come immediately
> > > >     after the bio_integrity_payload they're for, and there was an assignment
> > > >     in bio_integrity_split() that didn't make any sense.
> > > >     
> > > >     Also, changed bio_integrity_split() to not refer to the bvecs embedded
> > > >     in struct bio_pair, in case there's padding between them and
> > > >     bip->bip_vec.
> > > >     
> > > >     Signed-off-by: Kent Overstreet <koverstreet@...gle.com>
> > > >     CC: Jens Axboe <axboe@...nel.dk>
> > > >     CC: Martin K. Petersen <martin.petersen@...cle.com>
> > > > 
> > > > diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
> > > > index a3f28f3..4ae22a8 100644
> > > > --- a/fs/bio-integrity.c
> > > > +++ b/fs/bio-integrity.c
> > > > @@ -694,15 +694,12 @@ void bio_integrity_split(struct bio *bio, struct bio_pair *bp, int sectors)
> > > >  	bp->bio1.bi_integrity = &bp->bip1;
> > > >  	bp->bio2.bi_integrity = &bp->bip2;
> > > >  
> > > > -	bp->iv1 = bip->bip_vec[0];
> > > > -	bp->iv2 = bip->bip_vec[0];
> > > > +	*bp->bip1.bip_vec = bip->bip_vec[0];
> > > > +	*bp->bip2.bip_vec = bip->bip_vec[0];
> > > 
> > > I think this is horrible. Why not introduce bvec pointer in bip (like bio),
> > > to cover the case when bvec are not inline.
> > 
> > That's... exactly what the next patch in the series does.
> 
> Yes, but if you want to push some of the these bug fixes in stable (as martin
> had said), we need to introduce that bip->bio_vec pointer early. Also that
> next patch is doing lot other other things like getting rid of bip_slabs
> and we don't require all that to fix this particular bug.
> 
> In fact I would say that it is beter to fix this blk integrity bug in a
> separate patchset so that it can be pushed out earlier.

I'm honestly not sure what your complaint about my bugfix patch was -
it's small and complete, it does fix the bug. I don't follow why you
think we need to introduce the bip->bio_vec pointer early...
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