Re: [PATCH] RDS: IB: NULL dereference on error in rds_ib_alloc_frmr()

[Yuval Shaia <yuval.shaia-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On Wed, Jun 14, 2017 at 01:39:24PM +0300, Dan Carpenter wrote:
> We accidentally return ERR_PTR(0) if ib_alloc_mr() fails.  The caller
> is expecting error pointers so it results in a NULL dereference.
> 
> Fixes: 1659185fb4d0 ("RDS: IB: Support Fastreg MR (FRMR) memory registration mode")
> Signed-off-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> 
> diff --git a/net/rds/ib_frmr.c b/net/rds/ib_frmr.c
> index 48332a6ed738..74a66cc162ed 100644
> --- a/net/rds/ib_frmr.c
> +++ b/net/rds/ib_frmr.c
> @@ -38,7 +38,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
>  	struct rds_ib_mr_pool *pool;
>  	struct rds_ib_mr *ibmr = NULL;
>  	struct rds_ib_frmr *frmr;
> -	int err = 0;
> +	int err;

Can we trust it'll be zero?

>  
>  	if (npages <= RDS_MR_8K_MSG_SIZE)
>  		pool = rds_ibdev->mr_8k_pool;
> @@ -61,6 +61,7 @@ static struct rds_ib_mr *rds_ib_alloc_frmr(struct rds_ib_device *rds_ibdev,
>  			 pool->fmr_attr.max_pages);
>  	if (IS_ERR(frmr->mr)) {
>  		pr_warn("RDS/IB: %s failed to allocate MR", __func__);
> +		err = -ENOMEM;
>  		goto out_no_cigar;
>  	}
>  
> --
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