Re: [PATCH 1/1] cxl/pci: Check dport->regs.rcd_pcie_cap availability before accessing

[Alison Schofield]

On Fri, Nov 29, 2024 at 09:28:25PM +0800, Li Ming wrote:
> RCD Upstream Port's PCI Express Capability is a component registers
> block stored in RCD Upstream Port RCRB. CXL PCI driver helps to map it
> during the RCD probing, but mapping failure is allowed for component
> registers blocks in CXL PCI driver.
> 
> dport->regs.rcd_pcie_cap is used to store the virtual address of the RCD
> Upstream Port's PCI Express Capability, add a dport->regs.rcd_pcie_cap
> checking in rcd_pcie_cap_emit() just in case user accesses a invalid
> address via RCD sysfs.

I traced this enough to convince myself that dport cannot be NULL if
cxl_mem_find_port() succeeds. So, LGTM -

Reviewed-by: Alison Schofield <alison.schofield@xxxxxxxxx>

> 
> Fixes: c5eaec79fa43 ("cxl/pci: Add sysfs attribute for CXL 1.1 device link status")
> Signed-off-by: Li Ming <ming.li@xxxxxxxxxxxx>
> ---
>  drivers/cxl/pci.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index b2cb81f6d9e7..e53b1c95a248 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -836,6 +836,9 @@ static ssize_t rcd_pcie_cap_emit(struct device *dev, u16 offset, char *buf, size
>  	if (!root_dev)
>  		return -ENXIO;
>  
> +	if (!dport->regs.rcd_pcie_cap)
> +		return -ENXIO;
> +
>  	guard(device)(root_dev);
>  	if (!root_dev->driver)
>  		return -ENXIO;
> -- 
> 2.34.1
>