Re: [PATCH 6.13] PCI/pwrctrl: Skip NULL of_node when unregistering

[Jon Hunter <jonathanh@nvidia.com>]

On 26/11/2024 21:04, Brian Norris wrote:
> of_find_device_by_node() doesn't like a NULL pointer, and may end up
> identifying an arbitrary device, which we then start tearing down. We
> should check for NULL first.
> 
> Resolves issues seen when doing `echo 1 > /sys/bus/pci/devices/.../remove`:
> 
> [  222.952201] ------------[ cut here ]------------
> [  222.952218] WARNING: CPU: 0 PID: 5095 at drivers/regulator/core.c:5885 regulator_unregister+0x140/0x160
> ...
> [  222.953490] CPU: 0 UID: 0 PID: 5095 Comm: bash Tainted: G         C         6.12.0-rc1 #3
> ...
> [  222.954134] Call trace:
> [  222.954150]  regulator_unregister+0x140/0x160
> [  222.954186]  devm_rdev_release+0x1c/0x30
> [  222.954215]  release_nodes+0x68/0x100
> [  222.954249]  devres_release_all+0x98/0xf8
> [  222.954282]  device_unbind_cleanup+0x20/0x70
> [  222.954306]  device_release_driver_internal+0x1f4/0x240
> [  222.954333]  device_release_driver+0x20/0x40
> [  222.954358]  bus_remove_device+0xd8/0x170
> [  222.954393]  device_del+0x154/0x380
> [  222.954422]  device_unregister+0x28/0x88
> [  222.954451]  of_device_unregister+0x1c/0x30
> [  222.954488]  pci_stop_bus_device+0x154/0x1b0
> [  222.954521]  pci_stop_and_remove_bus_device_locked+0x28/0x48
> [  222.954553]  remove_store+0xa0/0xb8
> [  222.954589]  dev_attr_store+0x20/0x40
> [  222.954615]  sysfs_kf_write+0x4c/0x68
> [  222.954644]  kernfs_fop_write_iter+0x128/0x200
> [  222.954670]  do_iter_readv_writev+0xdc/0x1e0
> [  222.954709]  vfs_writev+0x100/0x2a0
> [  222.954742]  do_writev+0x84/0x130
> [  222.954773]  __arm64_sys_writev+0x28/0x40
> [  222.954808]  invoke_syscall+0x50/0x120
> [  222.954845]  el0_svc_common.constprop.0+0x48/0xf0
> [  222.954878]  do_el0_svc+0x24/0x38
> [  222.954910]  el0_svc+0x34/0xe0
> [  222.954945]  el0t_64_sync_handler+0x120/0x138
> [  222.954978]  el0t_64_sync+0x190/0x198
> [  222.955006] ---[ end trace 0000000000000000 ]---
> [  222.965216] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000c0
> ...
> [  223.107395] CPU: 3 UID: 0 PID: 5095 Comm: bash Tainted: G        WC         6.12.0-rc1 #3
> ...
> [  223.227750] Call trace:
> [  223.230501]  pci_stop_bus_device+0x190/0x1b0
> [  223.235314]  pci_stop_and_remove_bus_device_locked+0x28/0x48
> [  223.241672]  remove_store+0xa0/0xb8
> [  223.245616]  dev_attr_store+0x20/0x40
> [  223.249737]  sysfs_kf_write+0x4c/0x68
> [  223.253859]  kernfs_fop_write_iter+0x128/0x200
> [  223.253887]  do_iter_readv_writev+0xdc/0x1e0
> [  223.263631]  vfs_writev+0x100/0x2a0
> [  223.267550]  do_writev+0x84/0x130
> [  223.271273]  __arm64_sys_writev+0x28/0x40
> [  223.275774]  invoke_syscall+0x50/0x120
> [  223.279988]  el0_svc_common.constprop.0+0x48/0xf0
> [  223.285270]  do_el0_svc+0x24/0x38
> [  223.288993]  el0_svc+0x34/0xe0
> [  223.292426]  el0t_64_sync_handler+0x120/0x138
> [  223.297311]  el0t_64_sync+0x190/0x198
> [  223.301423] Code: 17fffff8 91030000 d2800101 f9800011 (c85f7c02)
> [  223.308248] ---[ end trace 0000000000000000 ]---
> 
> Fixes: 681725afb6b9 ("PCI/pwrctl: Remove pwrctl device without iterating over all children of pwrctl parent")
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
> 
>   drivers/pci/remove.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index 963b8d2855c1..efc37fcb73e2 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -19,14 +19,19 @@ static void pci_free_resources(struct pci_dev *dev)
>   
>   static void pci_pwrctrl_unregister(struct device *dev)
>   {
> +	struct device_node *np;
>   	struct platform_device *pdev;
>   
> -	pdev = of_find_device_by_node(dev_of_node(dev));
> +	np = dev_of_node(dev);
> +	if (!np)
> +		return;
> +
> +	pdev = of_find_device_by_node(np);
>   	if (!pdev)
>   		return;
>   
>   	of_device_unregister(pdev);
> -	of_node_clear_flag(dev_of_node(dev), OF_POPULATED);
> +	of_node_clear_flag(np, OF_POPULATED);
>   }
>   
>   static void pci_stop_dev(struct pci_dev *dev)


This fixes a regression we have been seeing on Tegra devices. FWIW ...

Tested-by: Jon Hunter <jonathanh@nvidia.com>

Thanks!
Jon

-- 
nvpublic