Re: [PATCH] RDMA/mana_ib: Prevent array underflow in mana_ib_create_qp_raw()

[Leon Romanovsky <leon@kernel.org>]

On Sun, Jan 29, 2023 at 01:27:07PM +0200, Leon Romanovsky wrote:
> On Fri, Jan 27, 2023 at 06:41:51AM +0000, Long Li wrote:
> > > Subject: Re: [PATCH] RDMA/mana_ib: Prevent array underflow in
> > > mana_ib_create_qp_raw()
> > > 
> > > On Thu, Jan 26, 2023 at 02:00:45PM +0300, Dan Carpenter wrote:
> > > > On Thu, Jan 26, 2023 at 12:18:46PM +0200, Leon Romanovsky wrote:
> > > > > On Tue, Jan 24, 2023 at 06:20:54PM +0300, Dan Carpenter wrote:
> > > > > > The "port" comes from the user and if it is zero then the:
> > > > > >
> > > > > > 	ndev = mc->ports[port - 1];
> > > > > >
> > > > > > assignment does an out of bounds read.  I have changed the if
> > > > > > statement to fix this and to mirror how it is done in
> > > > > > mana_ib_create_qp_rss().
> > > > > >
> > > > > > Fixes: 0266a177631d ("RDMA/mana_ib: Add a driver for Microsoft
> > > > > > Azure Network Adapter")
> > > > > > Signed-off-by: Dan Carpenter <error27@gmail.com>
> > > > > > ---
> > > > > >  drivers/infiniband/hw/mana/qp.c | 2 +-
> > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/drivers/infiniband/hw/mana/qp.c
> > > > > > b/drivers/infiniband/hw/mana/qp.c index ea15ec77e321..54b61930a7fd
> > > > > > 100644
> > > > > > --- a/drivers/infiniband/hw/mana/qp.c
> > > > > > +++ b/drivers/infiniband/hw/mana/qp.c
> > > > > > @@ -289,7 +289,7 @@ static int mana_ib_create_qp_raw(struct ib_qp
> > > > > > *ibqp, struct ib_pd *ibpd,
> > > > > >
> > > > > >  	/* IB ports start with 1, MANA Ethernet ports start with 0 */
> > > > > >  	port = ucmd.port;
> > > > > > -	if (ucmd.port > mc->num_ports)
> > > > > > +	if (port < 1 || port > mc->num_ports)
> > > > >
> > > > > Why do I see port in mana_ib_create_qp? It should come from ib_qp_init_attr.
> > > >
> > > > I am so confused by this question.  Are you asking me?
> > > 
> > > I asked *@microsoft folks.
> > > 
> > > > This is the _raw function.
> > > 
> > > _raw comes from QP type, it is not raw (basic) in a sense you imagine.
> > > 
> > > > I'm now sure what mana_ib_create_qp() has to do with it.
> > > 
> > > All create QP calls come through same verbs interface.
> > > ib_create_qp_user->create_qp->.create_qp->mana_ib_create_qp-
> > > >mana_ib_create_qp_raw
> > 
> > MANA requires passing a port number when creating a RAW QP on a RDMA(Ethernet) port.
> > At the hardware layer, the RDMA port and ethernet port share the same hardware resources, 
> > the port number needs to be known in advance when QP is created. If we don't' specify the port,
> > the QP needs to take all the ports on the MANA device, some of them may have been assigned to
> > Ethernet usage and can't be used for RDMA.
> > 
> > The reason is that unlike Nvidia CX hardware, MANA doesn't support bifurcation (for RAW QP) at the hardware level.
> > [https://www.dpdk.org/wp-content/uploads/sites/35/2018/06/Mellanox-bifurcated-driver-model.pdf]
> > To support RAW QP on a hardware port, we need to know the port number before configuring it on the hardware.
> > And Ethernet can't use this port if a RAW QP is created on it. The coordination needs to be done in software.
> > 
> > In production environment, there are multiple ports on the same MANA device assigned to a VM. Customer can
> > configure some of the ports for Ethernet and some for RDMA/DPDK.
> > 
> > I have investigated using the port_num in struct ib_qp_init_attr, but it seems it can't be used for this purpose
> > because the port needs to be specified by the user-mode.
> 
> And this is the most problematic part for me. I don't think that it is
> RDMA user responsibility to dig in netdev port numbers.

ok, I don't like it, but bug is here, let's fix it.

> 
> Jason, what do you think? It looks like layering violation.
> 
> Thanks
> 
> > 
> > Thanks,
> > Long
> > 
> > > 
> > > >
> > > > The port comes from ib_copy_from_udata() which is just a wrapper
> > > > around copy_from_user().
> > > 
> > > Right, and it shouldn't.
> > > 
> > > >
> > > > regards,
> > > > dan carpenter
> > > >