CVE-2024-49927

In the Linux kernel, the following vulnerability has been resolved:

x86/ioapic: Handle allocation failures gracefully

Breno observed panics when using failslab under certain conditions during runtime:

can not alloc irqpinlist (-1,0,20) Kernel panic - not syncing: IO-APIC: failed to add irq-pin. Can not proceed

panic+0x4e9/0x590 mpirqdomainalloc+0x9ab/0xa80 irqdomainallocirqslocked+0x25d/0x8d0 _irqdomainallocirqs+0x80/0x110 mpmappintoirq+0x645/0x890 acpiregistergsiioapic+0xe6/0x150 hpetopen+0x313/0x480

That's a pointless panic which is a leftover of the historic IO/APIC code which panic'ed during early boot when the interrupt allocation failed.

The only place which might justify panic is the PIT/HPET timer_check() code which tries to figure out whether the timer interrupt is delivered through the IO/APIC. But that code does not require to handle interrupt allocation failures. If the interrupt cannot be allocated then timer delivery fails and it either panics due to that or falls back to legacy mode.

Cure this by removing the panic wrapper around _addpintoirqnode() and making mpirqdomain_alloc() aware of the failure condition and handle it as any other failure in this function gracefully.