Re: [PATCH v2 1/3] ppc/pnv: Add null checks for OpenCapi PHBs

[Aditya Gupta <adityag@linux.ibm.com>]

On 08/06/26 21:09, Bjorn Helgaas wrote:

> On Wed, May 27, 2026 at 11:38:14PM +0530, Aditya Gupta wrote:
>> For opencapi phb direct slots, the .pdev for php_slots will be NULL
>>
>> Various sections of the code in pnv_php can do a null dereference and
>> crash the kernel.
>>
>> Originally, the issue was hit during boot:
>>
>>      [    1.568588] PowerPC PowerNV PCI Hotplug Driver version: 0.1
>>      [    1.569722] BUG: Kernel NULL pointer dereference at 0x00000074
>>      [    1.569811] Faulting instruction address: 0xc000000000b75fd0
>>      [    1.569890] Oops: Kernel access of bad area, sig: 11 [#1]
>>      [    1.569963] LE PAGE_SIZE=64K MMU=Hash  SMP NR_CPUS=2048 NUMA PowerNV
>>      ...
>>      [    1.571492] NIP [c000000000b75fd0] pnv_php_get_adapter_state+0x60/0x154
>>      [    1.571604] LR [c000000000b75fbc] pnv_php_get_adapter_state+0x4c/0x154
>>      [    1.571690] Call Trace:
>>      [    1.571725] [c000c0000688f990] [c000000000b75fbc] pnv_php_get_adapter_state+0x4c/0x154 (unreliable)
>>      [    1.571783] [c000c0000688fa20] [c000000000b78bd0] pnv_php_enable+0x94/0x378
>>      [    1.571951] [c000c0000688fac0] [c000000000b7912c] pnv_php_register_one.isra.0+0x11c/0x1e0
> Drop timestamps since they don't add useful information.
>
> Indent quoted material by two spaces to reduce wrapping.
>
> Run "git log --oneline drivers/pci/hotplug/pnv_php.c" and "git log
> --oneline drivers/pci/hotplug/" and match subject line style.
>
>> This occurs for hotplug slots on root buses where bus->self == NULL,
>> such as OpenCAPI PHB direct slots. An added debug print (not part of
>> this patch) confirmed it was opencapi:
> Style "OpenCAPI" and "PHB" consistently in commit log and subject.

Thanks for the review Bjorn, fixed the description and have sent the 
patch again as v3.

In v3, I have sent the patch #1 independently for rc, and will send the 
rework patches (patches #2 and #3) separately, since I have to do extra 
fixes for pre-existing issues pointed by sashiko.

Thanks,
- Aditya G