linux-kernel - Re: [PATCH] PCI/AER: Check for NULL aer_info before ratelimiting in pci_print

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Message-ID: <3kpkazpe4j4pws7rean5kelwmpfp5ij62psvdzvimcr37do47a@y2pvypskynno>
Date: Mon, 4 Aug 2025 08:35:19 -0700
From: Breno Leitao <leitao@...ian.org>
To: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: Mahesh J Salgaonkar <mahesh@...ux.ibm.com>, 
	Oliver O'Halloran <oohall@...il.com>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Jon Pan-Doh <pandoh@...gle.com>, linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH] PCI/AER: Check for NULL aer_info before ratelimiting in
 pci_print_aer()

Hello Sathyanarayanan,

On Mon, Aug 04, 2025 at 06:50:30AM -0700, Sathyanarayanan Kuppuswamy wrote:
> 
> On 8/4/25 2:17 AM, Breno Leitao wrote:
> > Similarly to pci_dev_aer_stats_incr(), pci_print_aer() may be called
> > when dev->aer_info is NULL. Add a NULL check before proceeding to avoid
> > calling aer_ratelimit() with a NULL aer_info pointer, returning 1, which
> > does not rate limit, given this is fatal.
> 
> Why not add it to pci_print_aer() ?
> 
> > 
> > This prevents a kernel crash triggered by dereferencing a NULL pointer
> > in aer_ratelimit(), ensuring safer handling of PCI devices that lack
> > AER info. This change aligns pci_print_aer() with pci_dev_aer_stats_incr()
> > which already performs this NULL check.
> 
> Is this happening during the kernel boot ? What is the frequency and steps
> to reproduce? I am curious about why pci_print_aer() is called for a PCI device
> without aer_info. Not aer_info means, that particular device is already released
> or in the process of release (pci_release_dev()). Is this triggered by using a stale
> pci_dev pointer?

I've reported some of these investigations in here:

https://lore.kernel.org/all/buduna6darbvwfg3aogl5kimyxkggu3n4romnmq6sozut6axeu@clnx7sfsy457/