CVE-2026-90332: PCI: dwc: ep: Flush cached MSI write before unmapping the iATU
In the Linux kernel, the following vulnerability has been resolved:
PCI: dwc: ep: Flush cached MSI write before unmapping the iATU
The MSI-X path already flushes any posted MSI-X write before tearing down its iATU mapping. That was added by commit c22533c66cca ("PCI: dwc: ep: Flush MSI-X write before unmapping its ATU entry") to make sure the write reaches the Root Complex before the outbound window that translates it disappears.
The MSI path has the same problem but no equivalent flush. When the Endpoint driver caches an MSI target address and later observes that the Root Complex has changed it, dwpcieepraisemsiirq() unmaps the existing iATU entry and reprograms it for the new address. Between the last MSI writel() and the unmap there may still be a posted write sitting in the fabric, and unmapping the iATU entry can drop or misroute that write.
Fix this by reading back from the mapped MSI window before the unmap. The readback drains any posted MSI writes through the same iATU entry that mapped them, which is the same logic the MSI-X path uses.
[mani: commit log]
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
It affects Linux systems using the DesignWare PCIe endpoint MSI path. The problematic sequence occurs when the endpoint driver has cached an MSI target address and the Root Complex changes that address.
What condition triggers the lost or misrouted interrupt risk?
A posted MSI write must still be pending when dw_pcie_ep_raise_msi_irq() removes the existing iATU mapping to program a new MSI target address. Removing the translation window before the write drains can cause that write to be dropped or routed incorrectly.
Does this also affect MSI-X interrupts?
The description states that the MSI-X path already reads back to flush posted MSI-X writes before its iATU mapping is removed. The missing equivalent flush was specific to the MSI path.
How can I determine whether the fix is present?
The corrected behavior reads back from the mapped MSI window before unmapping the existing iATU entry during MSI target-address changes. The referenced stable commits are 914704c7b318bdaa42dce4e55f6c492190fee3b5 and 1b01d725d8b42450b86a857bab3c46856c740166.