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-   -   block: Fix a buffer overrun in bio_integrity_split() (http://www.linux-archive.org/device-mapper-development/708908-block-fix-buffer-overrun-bio_integrity_split.html)

Vivek Goyal 10-01-2012 09:23 PM

block: Fix a buffer overrun in bio_integrity_split()
 
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@google.com>
> CC: Jens Axboe <axboe@kernel.dk>
> CC: Martin K. Petersen <martin.petersen@oracle.com>
> ---
> 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?

Also had a general question about split logic. We seem to have only one
global pool for bio pair (bio_split_pool). So in the IO stack if we split
a bio more than once, we have the deadlock possibility again?

Thanks
Vivek

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