rust: pci: reject IRQ vector indices that do not fit in u32

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@hotmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20260901-fix-pci-irq-vector-index-truncation-v4-1-f94aa6932fd9@hotmail.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 3 insertions, 1 deletions

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 @@ impl<'a> IrqVectorRegistration<'a> {
     /// [`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));
         }