linux-kernel - Re: Kernel 6.5-rc2: system crash on suspend bisected

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Date:   Mon, 24 Jul 2023 11:27:19 +0200
From:   Igor Mammedov <imammedo@...hat.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Woody Suwalski <terraluna977@...il.com>, bhelgaas@...gle.com,
        LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org,
        regressions@...ts.linux.dev
Subject: Re: Kernel 6.5-rc2: system crash on suspend bisected

On Thu, 20 Jul 2023 15:21:10 -0500
Bjorn Helgaas <helgaas@...nel.org> wrote:

> [+cc regressions list]
> 
> On Wed, Jul 19, 2023 at 11:36:51PM -0400, Woody Suwalski wrote:
> > Laptop shows a kernel crash trace after a first suspend to ram, on a second
> > attempt to suspend it becomes frozen solid. This is 100% repeatable with a
> > 6.5-rc2 kernel, not happening with a 6.4 kernel - see the attached dmesg
> > output.
> > 
> > I have bisected the kernel uilds and it points to :
> > [40613da52b13fb21c5566f10b287e0ca8c12c4e9] PCI: acpiphp: Reassign resources
> > on bridge if necessary
> > 
> > Reversing this patch seems to fix the kernel crash problem on my laptop.  
> 
> Thank you very much for all your work debugging, bisecting, and
> reporting this!  This is incredibly helpful.
> 
> Original report, including complete dmesg logs for both v6.4 and
> v6.5-rc2:
> https://lore.kernel.org/r/11fc981c-af49-ce64-6b43-3e282728bd1a@gmail.com
> 
> I queued up a revert of 40613da52b13 ("PCI: acpiphp: Reassign
> resources on bridge if necessary") (on my for-linus branch for v6.5).
> 
> It looks like a NULL pointer dereference; hopefully the fix is obvious
> and I can drop the revert and replace it with the fix.

it happens here:

2145	void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge)
2146	{
2147		struct pci_bus *parent = bridge->subordinate;

Let's see if it reproducable on Lenovo laptop and what reading
involved code yields.
If I can't figure it out anyways, I'll come up with a patch
to trace issue. 

> 
> Bjorn
>