Re: [dm-devel] [PATCH v3 01/26] block: Fix a buffer overrun in bio_integrity_split()

[Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>]

On Mon, Oct 01, 2012 at 05:23:36PM -0400, Vivek Goyal wrote:
> On Mon, Sep 24, 2012 at 03:34:41PM -0700, Kent Overstreet wrote:
> > 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.
> > 
> > Signed-off-by: Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> > CC: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
> > CC: Martin K. Petersen <martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> > ---
> >  fs/bio-integrity.c  | 3 ---
> >  include/linux/bio.h | 6 ++++--
> >  2 files changed, 4 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
> > index a3f28f3..c7b6b52 100644
> > --- a/fs/bio-integrity.c
> > +++ b/fs/bio-integrity.c
> > @@ -697,9 +697,6 @@ void bio_integrity_split(struct bio *bio, struct bio_pair *bp, int sectors)
> >  	bp->iv1 = bip->bip_vec[0];
> >  	bp->iv2 = bip->bip_vec[0];
> >  
> > -	bp->bip1.bip_vec[0] = bp->iv1;
> > -	bp->bip2.bip_vec[0] = bp->iv2;
> > -
> >  	bp->iv1.bv_len = sectors * bi->tuple_size;
> >  	bp->iv2.bv_offset += sectors * bi->tuple_size;
> >  	bp->iv2.bv_len -= sectors * bi->tuple_size;
> > diff --git a/include/linux/bio.h b/include/linux/bio.h
> > index b31036f..8e2d108 100644
> > --- a/include/linux/bio.h
> > +++ b/include/linux/bio.h
> > @@ -200,8 +200,10 @@ struct bio_pair {
> >  	struct bio			bio1, bio2;
> >  	struct bio_vec			bv1, bv2;
> >  #if defined(CONFIG_BLK_DEV_INTEGRITY)
> > -	struct bio_integrity_payload	bip1, bip2;
> > -	struct bio_vec			iv1, iv2;
> > +	struct bio_integrity_payload	bip1;
> > +	struct bio_vec			iv1;
> > +	struct bio_integrity_payload	bip2;
> > +	struct bio_vec			iv2;
> >  #endif
> 
> I think it probably is a good idea to put a comment here so that we
> know that certain elements of structure assume ordering.
> 
> Also I am wondering that what's the gurantee that there are no padding
> bytes between bipi1 and iv1 (or bip2 or iv2). I think if there are padding
> bytes then the assumption that bio_vec is always following bip will be
> broken?

Here's the new patch:


commit e270c9ca843b5c86d59431b0d7a676b7846946d6
Author: Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
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-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
    CC: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
    CC: Martin K. Petersen <martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>

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];
 
-	bp->bip1.bip_vec[0] = bp->iv1;
-	bp->bip2.bip_vec[0] = bp->iv2;
-
-	bp->iv1.bv_len = sectors * bi->tuple_size;
-	bp->iv2.bv_offset += sectors * bi->tuple_size;
-	bp->iv2.bv_len -= sectors * bi->tuple_size;
+	bp->bip1.bip_vec->bv_len = sectors * bi->tuple_size;
+	bp->bip2.bip_vec->bv_offset += sectors * bi->tuple_size;
+	bp->bip2.bip_vec->bv_len -= sectors * bi->tuple_size;
 
 	bp->bip1.bip_sector = bio->bi_integrity->bip_sector;
 	bp->bip2.bip_sector = bio->bi_integrity->bip_sector + nr_sectors;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b31036f..8e2d108 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -200,8 +200,10 @@ struct bio_pair {
 	struct bio			bio1, bio2;
 	struct bio_vec			bv1, bv2;
 #if defined(CONFIG_BLK_DEV_INTEGRITY)
-	struct bio_integrity_payload	bip1, bip2;
-	struct bio_vec			iv1, iv2;
+	struct bio_integrity_payload	bip1;
+	struct bio_vec			iv1;
+	struct bio_integrity_payload	bip2;
+	struct bio_vec			iv2;
 #endif
 	atomic_t			cnt;
 	int				error;