Re: [PATCH] LoongArch: KVM: Validate MSI data before routing it to EIOINTC

[Huacai Chen]

Applied, thanks.


Huacai

On Fri, Aug 28, 2026 at 5:36 PM Zeng Chi <zeng_chi911@xxxxxxx> wrote:
>
> From: Zeng Chi <zengchi@xxxxxxxxxx>
>
> pch_msi_set_irq() passes e->msi.data straight into eiointc_set_irq() as
> the irq number.  The MSI data comes from userspace, either via a
> KVM_IRQ_ROUTING_MSI entry set with KVM_SET_GSI_ROUTING (used by irqfd
> and KVM_IRQ_LINE) or directly via KVM_SIGNAL_MSI, and is never checked
> against EIOINTC_IRQS.
>
> eiointc_set_irq() uses the value with __set_bit()/__clear_bit() on the
> 256-bit isr bitmap, eiointc_update_irq() then indexes sw_coremap[] and
> the per-cpu coreisr/sw_coreisr bitmaps with it.  A data value >= 256
> therefore reads and writes memory past the end of those arrays, i.e.
> any process holding a VM fd can corrupt kernel memory beyond the
> loongarch_eiointc allocation.
>
> Reject MSI data that doesn't fit in the EIOINTC irq space.  The DMSINTC
> path is unaffected as it decodes the vector from the address and masks
> it.
>
> Fixes: 1928254c5ccb ("LoongArch: KVM: Add irqfd support")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Closes: https://lore.kernel.org/all/20260531140921.1B1181F00893@xxxxxxxxxxxxxxx/
> Signed-off-by: Zeng Chi <zengchi@xxxxxxxxxx>
> ---
>  arch/loongarch/kvm/intc/pch_pic.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/loongarch/kvm/intc/pch_pic.c b/arch/loongarch/kvm/intc/pch_pic.c
> index e7b77705c516..81fb534ce8dd 100644
> --- a/arch/loongarch/kvm/intc/pch_pic.c
> +++ b/arch/loongarch/kvm/intc/pch_pic.c
> @@ -78,6 +78,9 @@ int pch_msi_set_irq(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e, int
>                 return dmsintc_set_irq(kvm, msg_addr, e->msi.data, level);
>         }
>
> +       if (e->msi.data >= EIOINTC_IRQS)
> +               return -EINVAL;
> +
>         eiointc_set_irq(kvm->arch.eiointc, e->msi.data, level);
>
>         return 0;
> --
> 2.25.1
>
>
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>