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

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Message-ID: <20251001213657.GA241794@bhelgaas>
Date: Wed, 1 Oct 2025 16:36:57 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
	Oliver O'Halloran <oohall@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.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, stable@...r.kernel.org
Subject: Re: [PATCH RESEND] PCI/AER: Check for NULL aer_info before
 ratelimiting in pci_print_aer()

On Mon, Sep 29, 2025 at 02:15:47AM -0700, 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.
> 
> 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.
> 
> Cc: stable@...r.kernel.org
> Fixes: a57f2bfb4a5863 ("PCI/AER: Ratelimit correctable and non-fatal error logging")
> Signed-off-by: Breno Leitao <leitao@...ian.org>

Thanks, Breno, I applied this to pci/aer for v6.18.  I added a little
more detail to the commit log because the path where we hit this is a
bit obscure.  Please take a look and see if it makes sense:

  https://git.kernel.org/cgit/linux/kernel/git/pci/pci.git/commit/?id=451f30b97807

> ---
> - This problem is still happening in upstream, and unfortunately no action
>   was done in the previous discussion.
> - Link to previous post:
>   https://lore.kernel.org/r/20250804-aer_crash_2-v1-1-fd06562c18a4@debian.org
> ---
>  drivers/pci/pcie/aer.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index e286c197d7167..55abc5e17b8b1 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -786,6 +786,9 @@ static void pci_rootport_aer_stats_incr(struct pci_dev *pdev,
>  
>  static int aer_ratelimit(struct pci_dev *dev, unsigned int severity)
>  {
> +	if (!dev->aer_info)
> +		return 1;
> +
>  	switch (severity) {
>  	case AER_NONFATAL:
>  		return __ratelimit(&dev->aer_info->nonfatal_ratelimit);
> 
> ---
> base-commit: e5f0a698b34ed76002dc5cff3804a61c80233a7a
> change-id: 20250801-aer_crash_2-b21cc2ef0d00
> 
> Best regards,
> --  
> Breno Leitao <leitao@...ian.org>
>