Re: [PATCH] IB/rdmavt: Only put mmap_info ref if it exists

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Tue, Nov 01, 2016 at 01:44:12PM -0700, Jim Foraker wrote:
> rvt_create_qp() creates qp->ip only when a qp creation request comes from
> userspace (udata is not NULL).  If we exceed the number of available
> queue pairs however, the error path always attempts to put a kref to this
> structure.  If the requestor is inside the kernel, this leads to a crash.

It will be great to have a crash report if you have one.

>
> We fix this by checking that qp->ip is not NULL before caling kref_put().
>

Please add Fixes line which refers to the commit you are fixing.
It will ensure automatic pickup to various stable trees.

Thanks

> Signed-off-by: Jim Foraker <foraker1-i2BcT+NCU+M@public.gmane.org>
> ---
>  drivers/infiniband/sw/rdmavt/qp.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
> index 6500c3b..0004e8b 100644
> --- a/drivers/infiniband/sw/rdmavt/qp.c
> +++ b/drivers/infiniband/sw/rdmavt/qp.c
> @@ -884,7 +884,8 @@ struct ib_qp *rvt_create_qp(struct ib_pd *ibpd,
>  	return ret;
>
>  bail_ip:
> -	kref_put(&qp->ip->ref, rvt_release_mmap_info);
> +	if (qp->ip)
> +		kref_put(&qp->ip->ref, rvt_release_mmap_info);
>
>  bail_qpn:
>  	free_qpn(&rdi->qp_dev->qpn_table, qp->ibqp.qp_num);
> --
> 1.7.1
>
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