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SubjectRe: [PATCH 3/4] vfio: ccw: set ccw->cda to NULL defensively
On Wed, 21 Mar 2018 03:08:21 +0100
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> Let's avoid free on ccw->cda that points to a guest address
> or a already freed memory area by setting it to NULL if memory
> allocation didn't happen or failed.

Does not hurt, I guess.

>
> Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> ---
> drivers/s390/cio/vfio_ccw_cp.c | 28 +++++++++++++++++++---------
> 1 file changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
> index 3abc9770910a..5958c35ab343 100644
> --- a/drivers/s390/cio/vfio_ccw_cp.c
> +++ b/drivers/s390/cio/vfio_ccw_cp.c
> @@ -491,7 +491,7 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
> struct ccw1 *ccw;
> struct pfn_array_table *pat;
> unsigned long *idaws;
> - int idaw_nr;
> + int idaw_nr, ret;
>
> ccw = chain->ch_ccw + idx;
>
> @@ -511,18 +511,20 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
> * needed when translating a direct ccw to a idal ccw.
> */
> pat = chain->ch_pat + idx;
> - if (pfn_array_table_init(pat, 1))
> - return -ENOMEM;
> - idaw_nr = pfn_array_alloc_pin(pat->pat_pa, cp->mdev,
> + ret = pfn_array_table_init(pat, 1);
> + if (ret)
> + goto out_init;
> +
> + idaw_nr = ret = pfn_array_alloc_pin(pat->pat_pa, cp->mdev,

Ugh, I don't like setting both at the same time... only set idaw_nr for
ret > 0? (personal preference)

> ccw->cda, ccw->count);
> - if (idaw_nr < 0)
> - return idaw_nr;
> + if (ret < 0)
> + goto out_init;

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