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

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Message-ID: <20241012143119.GA604156@bhelgaas>
Date: Sat, 12 Oct 2024 09:31:19 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH v2] PCI: take the rescan lock when adding devices during
 host probe

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@...ev.pl> wrote:
> >
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > 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@...nel.org>
> > Tested-by: Konrad Dybcio <konradybcio@...nel.org>
> > Fixes: 4565d2652a37 ("PCI/pwrctl: Add PCI power control core code")
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > ---
> 
> 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.

Bjorn