FAILED: patch "[PATCH] LoongArch: KVM: Validate MSI data before routing it to" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 501514d6ebd2111c353a1296f25dbe22fbd64657
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090955-troubling-exposure-3a3b@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 501514d6ebd2111c353a1296f25dbe22fbd64657 Mon Sep 17 00:00:00 2001
From: Zeng Chi <[email protected]>
Date: Fri, 4 Sep 2026 21:45:13 +0800
Subject: [PATCH] LoongArch: KVM: Validate MSI data before routing it to
EIOINTC

pch_msi_set_irq() passes e->msi.data straight into eiointc_set_irq() as the irq number. The MSI data comes from userspace, that 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. Therefore a data value

process holding a VM fd can corrupt kernel memory beyond the allocation of loongarch_eiointc.

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.

index 83fa2386cf81..2b63b0c2c7ce 100644
@@ -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;