Re: [PATCH] PCI/AER: Check for NULL aer_info before ratelimiting in pci_print_aer()

[Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>]

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?

>
> Signed-off-by: Breno Leitao <leitao@debian.org>
> Fixes: a57f2bfb4a5863 ("PCI/AER: Ratelimit correctable and non-fatal error logging")
> ---
>   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 70ac661883672..b5f96fde4dcda 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: 89748acdf226fd1a8775ff6fa2703f8412b286c8
> change-id: 20250801-aer_crash_2-b21cc2ef0d00
>
> Best regards,
> --
> Breno Leitao <leitao@debian.org>
>
-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer