Re: [PATCH 2/2] cxl/core/regs: Check return value of DVSEC register locator reads

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The newly added early returns on `pci_read_config_dword()` failures leak intermediate register block state in the `map` output parameter. If a previous loop iteration successfully decoded a non-matching block, that state is retained and erroneously consumed by callers that ignore the return value.
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commit 33d355daa1f588d8fa2e0001a3651a368f36be29
Author: Richard Cheng <icheng@nvidia.com>

cxl/core/regs: Check return value of DVSEC register locator reads

This commit checks the return value of pci_read_config_dword() when
reading the CXL Register Locator DVSEC. On failure, it converts the
PCIBIOS status to a negative errno to avoid decoding register block
addresses from garbage data.

> diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c
> --- a/drivers/cxl/core/regs.c
> +++ b/drivers/cxl/core/regs.c
[ ... ]
> @@ -324,8 +326,12 @@ static int __cxl_find_regblock_instance(struct pci_dev *pdev, enum cxl_regloc_ty
>  	for (i = 0; i < regblocks; i++, regloc += 8) {
>  		u32 reg_lo, reg_hi;
>  
> -		pci_read_config_dword(pdev, regloc, &reg_lo);
> -		pci_read_config_dword(pdev, regloc + 4, &reg_hi);
> +		rc = pci_read_config_dword(pdev, regloc, &reg_lo);
> +		if (rc)
> +			return pcibios_err_to_errno(rc);

[Severity: High]
Does this early return leave map->resource populated with stale data?

If a previous loop iteration successfully decoded a non-matching block
(such as CXL_REGLOC_RBI_MEMDEV), map->resource and map->reg_type will
be populated. If a subsequent config read fails, returning early bypasses
the map->resource = CXL_RESOURCE_NONE cleanup at the end of the function.

Callers like find_component_registers() in drivers/cxl/core/port.c ignore
the return value of cxl_find_regblock() and blindly consume map.resource.
Will this cause the caller to erroneously map the wrong registers (like
the memdev registers) as component registers?

> +		rc = pci_read_config_dword(pdev, regloc + 4, &reg_hi);
> +		if (rc)
> +			return pcibios_err_to_errno(rc);
>  
>  		if (!cxl_decode_regblock(pdev, reg_lo, reg_hi, map))
>  			continue;

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Sashiko AI review · https://sashiko.dev/#/patchset/20260607070241.48978-1-icheng@nvidia.com?part=2