PCI: pciehp: Fix infinite loop in IRQ handler upon power fault

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.

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于 PCI:pciehp 模块电源故障时 IRQ 处理程序会发生无限循环。

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