linux-kernel - Re: [PATCH] PCI/AER: Fix NULL pointer access by aer

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Message-ID: <20250911225457.GA1596803@bhelgaas>
Date: Thu, 11 Sep 2025 17:54:57 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Vernon Yang <vernon2gm@...il.com>
Cc: mahesh@...ux.ibm.com, bhelgaas@...gle.com, oohall@...il.com,
	linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Vernon Yang <yanglincheng@...inos.cn>,
	Terry Bowman <terry.bowman@....com>,
	Robert Richter <rrichter@....com>, linux-cxl@...r.kernel.org,
	Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
	Dongdong Liu <liudongdong3@...wei.com>
Subject: Re: [PATCH] PCI/AER: Fix NULL pointer access by aer_info

[+cc Terry, Robert, CXL list, Smita, Dongdong]

On Fri, Sep 05, 2025 at 02:25:27AM +0800, Vernon Yang wrote:
> From: Vernon Yang <yanglincheng@...inos.cn>
> 
> The kzalloc(GFP_KERNEL) may return NULL, so all accesses to
> aer_info->xxx will result in kernel panic. Fix it.
> 
> Signed-off-by: Vernon Yang <yanglincheng@...inos.cn>

Applied to pci/aer for v6.18, thanks, Vernon!

Not directly related to this patch, but I'm concerned about some users
of dev->aer_cap.

Most users of dev->aer_cap either (a) check that it's set before using
it or (b) are called in paths obviously only reachable via an AER
interrupt.

But there are a few users of dev->aer_cap that use it without checking
it for zero, and it's not obvious to me that it must be valid:

  - pci_aer_unmask_internal_errors(), added by b7e9392d5d46 ("PCI/AER:
    Unmask RCEC internal errors to enable RCH downstream port error
    handling")

  - dpc_get_aer_uncorrect_severity(), added by 9f08a5d896ce ("PCI/DPC:
    Fix print AER status in DPC event handling")

  - dpc_is_surprise_removal(), added by 2ae8fbbe1cd4 ("PCI/DPC: Ignore
    Surprise Down error on hot removal")

> ---
>  drivers/pci/pcie/aer.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index e286c197d716..aeb2534f50dd 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -383,6 +383,10 @@ void pci_aer_init(struct pci_dev *dev)
>  		return;
>  
>  	dev->aer_info = kzalloc(sizeof(*dev->aer_info), GFP_KERNEL);
> +	if (!dev->aer_info) {
> +		dev->aer_cap = 0;
> +		return;
> +	}
>  
>  	ratelimit_state_init(&dev->aer_info->correctable_ratelimit,
>  			     DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
> -- 
> 2.51.0
>