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

[Yuval Shaia <yuval.shaia@oracle.com>]

On Wed, Jun 14, 2017 at 04:03:40PM +0300, Dan Carpenter wrote:
> On Wed, Jun 14, 2017 at 03:54:24PM +0300, Yuval Shaia wrote:
> > 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@oracle.com>
> > > 
> > > 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?
> 
> We don't ever want it to be zero.  This way, hopefully, GCC will catch
> it if we introduce any new bugs where we forget to set it to negative.

I see your point, in a "good" case we just return the ptr.

Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>

> 
> regards,
> dan carpenter
>