Affected: Linux

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

LoongArch: KVM: Mark hrtimer to expire in hard interrupt context

Like commit 2c0d278f3293f ("KVM: LAPIC: Mark hrtimer to expire in hard interrupt context") and commit 9090825fa9974 ("KVM: arm/arm64: Let the timer expire in hardirq context on RT"), On PREEMPT_RT enabled kernels unmarked hrtimers are moved into soft interrupt expiry mode by default. Then the timers are canceled from an preempt-notifier which is invoked with disabled preemption which is not allowed on PREEMPT_RT.

The timer callback is short so in could be invoked in hard-IRQ context. So let the timer expire on hard-IRQ context even on -RT.

This fix a "scheduling while atomic" bug for PREEMPT_RT enabled kernels:

BUG: scheduling while atomic: qemu-system-loo/1011/0x00000002 Modules linked in: amdgpu rfkill nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat ns CPU: 1 UID: 0 PID: 1011 Comm: qemu-system-loo Tainted: G W 6.12.0-rc2+ #1774 Tainted: [W]=WARN Hardware name: Loongson Loongson-3A5000-7A1000-1w-CRB/Loongson-LS3A5000-7A1000-1w-CRB, BIOS vUDK2018-LoongArch-V2.0.0-prebeta9 10/21/2022 Stack : ffffffffffffffff 0000000000000000 9000000004e3ea38 9000000116744000 90000001167475a0 0000000000000000 90000001167475a8 9000000005644830 90000000058dc000 90000000058dbff8 9000000116747420 0000000000000001 0000000000000001 6a613fc9…