linux-kernel - Re: [PATCH] RDMA/core: fix a NULL-pointer dereference in hw_stat_device

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Message-ID: <Z76NUKn6SCrrw1vt@google.com>
Date: Wed, 26 Feb 2025 03:41:04 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Parav Pandit <parav@...lanox.com>
Cc: Jason Gunthorpe <jgg@...dia.com>, Leon Romanovsky <leon@...nel.org>,
	Maher Sanalla <msanalla@...dia.com>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RDMA/core: fix a NULL-pointer dereference in
 hw_stat_device_show()

On Tue, Feb 25, 2025 at 04:34:11AM +0000, Parav Pandit wrote:
> 
> 
> > From: Roman Gushchin <roman.gushchin@...ux.dev>
> > Sent: Tuesday, February 25, 2025 9:12 AM
> > 
> > On Mon, Feb 24, 2025 at 07:30:04PM -0400, Jason Gunthorpe wrote:
> > > On Mon, Feb 24, 2025 at 11:22:29PM +0000, Roman Gushchin wrote:
> > > > On Mon, Feb 24, 2025 at 03:16:46PM +0000, Parav Pandit wrote:
> > > > >
> > > > >
> > > > > > From: Jason Gunthorpe <jgg@...dia.com>
> > > > > > Sent: Monday, February 24, 2025 8:41 PM
> > > > > >
> > > > > > On Sat, Feb 22, 2025 at 06:34:21PM +0000, Parav Pandit wrote:
> > > > > > > ib_setup_device_attrs() should be merged to
> > > > > > > ib_setup_port_attrs() by renaming ib_setup_port_attrs() to be
> > > > > > > generic.  To utilize the group initialization
> > > > > > > ib_setup_port_attrs() needs to move up before device_add().
> > > > > >
> > > > > > It needs more than that, somehow you have to maintain two groups
> > > > > > list or somehow remove the coredev->dev.groups assignment..
> > > > > >
> > > > > I was thinking that if both device and port attr setup is done in
> > > > > same function, there is knowledge of is_full_dev that can be used
> > > > > for device level hw_stats setup. (similar to how its done at port
> > > > > level).
> > > >
> > > > Given that there is a bit of discussion on how to move forward with
> > > > this, can we please merge the trivial fix in the mean time? (Just
> > > > sent out v2 with the fixed commit log).
> > >
> > > Well, the issue now is the ABI break
> > >
> > > If the right answer is to remove the sysfs entirely then it doesn't
> > > make sense to make it work in the stable and LTS kernels since that
> > > would create users. Currently it is fully broken so there are no
> > > users. Can we say that so certainly after it is fixed?
> > 
> > It's a good point.
> > 
> > Ok, then we need something like this (obviously, coded more nicely):
> > 
> Yes, this is my suggestion too in little more detail at [1].
> 
> [1] https://lore.kernel.org/linux-rdma/20250224233109.GE520155@nvidia.com/T/#m43a5974cad17566080eeb64c6d5327aad4f0a852

I tried to implement what you suggested, but apparently it's complicated.
You can't call ib_setup_port_attrs() before device_add() because
kobject_init_and_add() fails. Maybe an option is to add "hw_counters"
dynamically similar to ports, Idk.

Anyway, sent a slightly different version, please, take a look.

Thanks!