Re: [PATCH v4] rust: pci: reject IRQ vector indices that do not fit in u32

[Gary Guo]

On Mon Aug 31, 2026 at 6:09 PM BST, Sophon Zhang via B4 Relay wrote:
> From: Sophon Zhang <aiqubits@xxxxxxxxxxx>
> 
> IrqVectorRegistration::index() accepts a usize, but pci_irq_vector()
> takes an unsigned int. On 64-bit architectures, casting an index larger
> than u32::MAX wraps it before the PCI core can validate it. In
> particular, u32::MAX + 1 becomes zero and can resolve to the first
> allocated vector.
> 
> Use a checked conversion and return EINVAL when the index cannot be
> represented by the C API.
> 
> Fixes: 2fb7755b0a7e ("rust: pci: resolve IRQ in index() and embed IrqRequest in IrqVector")
> Signed-off-by: Sophon Zhang <aiqubits@xxxxxxxxxxx>

Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>

> ---
> Prevent 64-bit Rust IRQ vector indices from wrapping when they cross the
> PCI C API boundary.
> ---
> Changes in v4:
> - Drop the explicit length check in favor of PCI core range validation.
> - Use the existing TryFromIntError-to-Error conversion directly.
> - Keep commit trailers adjacent and narrow the description to truncation.
> - Link to v3: https://patch.msgid.link/20260831-fix-pci-irq-vector-index-truncation-v3-1-a2103084d20e@xxxxxxxxxxx
> 
> Changes in v3:
> - Check the index against the allocated vector count before entering the C API.
> - Keep the checked usize-to-u32 conversion and document the C-side warning.
> - Link to v2: https://patch.msgid.link/20260831-fix-pci-irq-vector-index-truncation-v2-1-4030ea7746a9@xxxxxxxxxxx
> 
> Changes in v2:
> - No code changes.
> - Link to v1: https://patch.msgid.link/20260831-fix-pci-irq-vector-index-truncation-v1-1-d63217d99b67@xxxxxxxxxxx
> 
> Testing:
> - make rustfmtcheck
> - Not build- or hardware-tested; bindgen is unavailable in the test environment.
> ---
>  rust/kernel/pci/irq.rs | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)