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

[Sophon Zhang via B4 Relay]

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>
---
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(-)

diff --git a/rust/kernel/pci/irq.rs b/rust/kernel/pci/irq.rs
index 6741046ec1c0..22e2cdf82a21 100644
--- a/rust/kernel/pci/irq.rs
+++ b/rust/kernel/pci/irq.rs
@@ -151,8 +151,10 @@ pub fn irq_type(&self) -> IrqType {
     /// [`Self::len()`].
     #[inline]
     pub fn index(&self, index: usize) -> Result<IrqVector<'_>> {
+        let index = u32::try_from(index)?;
+
         // SAFETY: `self.dev.as_raw()` is a valid pointer to a `struct pci_dev`.
-        let irq = unsafe { bindings::pci_irq_vector(self.dev.as_raw(), index as u32) };
+        let irq = unsafe { bindings::pci_irq_vector(self.dev.as_raw(), index) };
         if irq < 0 {
             return Err(Error::from_errno(irq));
         }

---
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
change-id: 20260831-fix-pci-irq-vector-index-truncation-6752f3751a0d

Best regards,
--  
Sophon Zhang <aiqubits@xxxxxxxxxxx>