Re: [PATCH v2] PCI: take the rescan lock when adding devices during host probe

[Bartosz Golaszewski]

On Sat, Oct 12, 2024 at 4:31 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>
> On Thu, Oct 10, 2024 at 11:17:47AM +0200, Bartosz Golaszewski wrote:
> > On Thu, Oct 3, 2024 at 10:43 AM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> > >
> > > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > >
> > > Since adding the PCI power control code, we may end up with a race
> > > between the pwrctl platform device rescanning the bus and the host
> > > controller probe function. The latter needs to take the rescan lock when
> > > adding devices or we may end up in an undefined state having two
> > > incompletely added devices and hit the following crash when trying to
> > > remove the device over sysfs:
> > >
> > > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> > > Internal error: Oops: 0000000096000004 [#1] SMP
> > > Call trace:
> > >   __pi_strlen+0x14/0x150
> > >   kernfs_find_ns+0x80/0x13c
> > >   kernfs_remove_by_name_ns+0x54/0xf0
> > >   sysfs_remove_bin_file+0x24/0x34
> > >   pci_remove_resource_files+0x3c/0x84
> > >   pci_remove_sysfs_dev_files+0x28/0x38
> > >   pci_stop_bus_device+0x8c/0xd8
> > >   pci_stop_bus_device+0x40/0xd8
> > >   pci_stop_and_remove_bus_device_locked+0x28/0x48
> > >   remove_store+0x70/0xb0
> > >   dev_attr_store+0x20/0x38
> > >   sysfs_kf_write+0x58/0x78
> > >   kernfs_fop_write_iter+0xe8/0x184
> > >   vfs_write+0x2dc/0x308
> > >   ksys_write+0x7c/0xec
> > >
> > > Reported-by: Konrad Dybcio <konradybcio@xxxxxxxxxx>
> > > Tested-by: Konrad Dybcio <konradybcio@xxxxxxxxxx>
> > > Fixes: 4565d2652a37 ("PCI/pwrctl: Add PCI power control core code")
> > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > > ---
> >
> > It's been a week, so gentle ping - can this be picked up into v6.12?
>
> I hoped we could fix the similar latent issues in other drivers, but
> yes, we can get this in v6.12.  Thanks for the hint that it should go
> there.  I'll pick it up when I return from vacation on Wednesday.
>

Sure this can still be done but this patch fixes an urgent issue and I
think it warrants fast tracking it to mainline.

Bart