RE: [PATCH] vdpa_sim: avoid putting an uninitialized iova_domain

[Longpeng (Mike, Cloud Infrastructure Service Product Dept.)]

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@xxxxxxxxxx]
> Sent: Tuesday, November 23, 2021 12:13 PM
> To: Parav Pandit <parav@xxxxxxxxxx>
> Cc: Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
> <longpeng2@xxxxxxxxxx>; mst@xxxxxxxxxx; sgarzare@xxxxxxxxxx; Max Gurtovoy
> <mgurtovoy@xxxxxxxxxx>; virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; Gonglei (Arei) <arei.gonglei@xxxxxxxxxx>
> Subject: Re: [PATCH] vdpa_sim: avoid putting an uninitialized iova_domain
> 
> On Tue, Nov 23, 2021 at 11:12 AM Parav Pandit <parav@xxxxxxxxxx> wrote:
> >
> >
> >
> > > From: Longpeng(Mike) <longpeng2@xxxxxxxxxx>
> > > Sent: Monday, November 22, 2021 5:52 PM
> > >
> > > From: Longpeng <longpeng2@xxxxxxxxxx>
> > >
> > > The system will crash if we put an uninitialized iova_domain, this could
> > > happen when an error occurs before initializing the iova_domain in
> > > vdpasim_create().
> > >
> > > BUG: kernel NULL pointer dereference, address: 0000000000000000 ...
> > > RIP: 0010:__cpuhp_state_remove_instance+0x96/0x1c0
> > > ...
> > > Call Trace:
> > >  <TASK>
> > >  put_iova_domain+0x29/0x220
> > >  vdpasim_free+0xd1/0x120 [vdpa_sim]
> > >  vdpa_release_dev+0x21/0x40 [vdpa]
> > >  device_release+0x33/0x90
> > >  kobject_release+0x63/0x160
> > >  vdpasim_create+0x127/0x2a0 [vdpa_sim]
> > >  vdpasim_net_dev_add+0x7d/0xfe [vdpa_sim_net]
> > >  vdpa_nl_cmd_dev_add_set_doit+0xe1/0x1a0 [vdpa]
> > >  genl_family_rcv_msg_doit+0x112/0x140
> > >  genl_rcv_msg+0xdf/0x1d0
> > >  ...
> > >
> > > So we must make sure the iova_domain is already initialized before put it.
> > >
> > > In addition, we may get the following warning in this case:
> > > WARNING: ... drivers/iommu/iova.c:344 iova_cache_put+0x58/0x70
> > >
> > > So we must make sure the iova_cache_put() is invoked only if the
> > > iova_cache_get() is already invoked. Let's fix it together.
> > >
> > > Signed-off-by: Longpeng <longpeng2@xxxxxxxxxx>
> >
> > Can you please add the fixes tag here so that older kernels can take this fix?
> >
> 
> I guess it's 4080fc106750 ("vdpa_sim: use iova module to allocate IOVA
> addresses")
> 

I think so. I'll add the fixes tag in V2, thanks.

> Thanks