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

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Message-ID: <Z708JNt6-vPIuDBm@google.com>
Date: Tue, 25 Feb 2025 03:42:28 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Parav Pandit <parav@...lanox.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 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):

diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
index 0ded91f056f3..6998907fc779 100644
--- a/drivers/infiniband/core/device.c
+++ b/drivers/infiniband/core/device.c
@@ -956,6 +956,7 @@ static int add_one_compat_dev(struct ib_device *device,
        ret = device_add(&cdev->dev);
        if (ret)
                goto add_err;
+       device->groups[2] = NULL;
        ret = ib_setup_port_attrs(cdev);
        if (ret)
                goto port_err;