linux-kernel - Re: [PATCH] media: cobalt: fix null-ptr-deref when there is no PCI bridge

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Date:   Wed, 5 May 2021 11:18:14 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Tong Zhang <ztong0001@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: cobalt: fix null-ptr-deref when there is no PCI
 bridge

On 24/04/2021 02:52, Tong Zhang wrote:
> the PCI bridge might be NULL, so we'd better check before use it
> 
> [    1.870569] RIP: 0010:pcie_bus_link_get_lanes.isra.0+0x26/0x59 [cobalt]
> [    1.875880] Call Trace:
> [    1.876013]  cobalt_probe.cold+0x1be/0xc11 [cobalt]
> [    1.876683]  pci_device_probe+0x10f/0x1c0

How did you test this? With some virtualized PCI bus or something? I'm not sure
how this can happen.

Regards,

	Hans

> 
> Signed-off-by: Tong Zhang <ztong0001@...il.com>
> ---
>  drivers/media/pci/cobalt/cobalt-driver.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/media/pci/cobalt/cobalt-driver.c b/drivers/media/pci/cobalt/cobalt-driver.c
> index 0695078ef812..5687ed4869ac 100644
> --- a/drivers/media/pci/cobalt/cobalt-driver.c
> +++ b/drivers/media/pci/cobalt/cobalt-driver.c
> @@ -189,6 +189,8 @@ void cobalt_pcie_status_show(struct cobalt *cobalt)
>  	u32 capa;
>  	u16 stat, ctrl;
>  
> +	if (!pci_bus_dev)
> +		return;
>  	if (!pci_is_pcie(pci_dev) || !pci_is_pcie(pci_bus_dev))
>  		return;
>  
> @@ -247,6 +249,8 @@ static unsigned pcie_bus_link_get_lanes(struct cobalt *cobalt)
>  	struct pci_dev *pci_dev = cobalt->pci_dev->bus->self;
>  	u32 link;
>  
> +	if (!pci_dev)
> +		return 0;
>  	if (!pci_is_pcie(pci_dev))
>  		return 0;
>  	pcie_capability_read_dword(pci_dev, PCI_EXP_LNKCAP, &link);
>