In the Linux kernel, the following vulnerability has been resolved:
powerpc/smp: do not decrement idle task preempt count in CPU offline
With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we get:
BUG: scheduling while atomic: swapper/1/0/0x00000000 no locks held by swapper/1/0. CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100 Call Trace: dump_stack_lvl+0xac/0x108 __schedule_bug+0xac/0xe0 __schedule+0xcf8/0x10d0 schedule_idle+0x3c/0x70 do_idle+0x2d8/0x4a0 cpu_startup_entry+0x38/0x40 start_secondary+0x2ec/0x3a0 start_secondary_prolog+0x10/0x14
This is because powerpcs arch_cpu_idle_dead() decrements the idle tasks preempt count, for reasons explained in commit a7c2bb8279d2 (powerpc: Re-enable preemption before cpu_die()), specifically start_secondary() expects a preempt_count() of 0.
However, since commit 2c669ef6979c (powerpc/preempt: Dont touch the idle tasks preempt_count during hotplug) and commit f1a0a376ca0c (sched/core: Initialize the idle task with preemption disabled), that justification no longer holds.
The idle task isnt supposed to re-enable preemption, so remove the vestigial preempt_enable() from the CPU offline path.
Tested with pseries and powernv in qemu, and pseries on PowerVM.
Name | Vendor | Start Version | End Version |
---|---|---|---|
Linux | Ubuntu | upstream | * |
Linux-allwinner-5.19 | Ubuntu | jammy | * |
Linux-allwinner-5.19 | Ubuntu | upstream | * |
Linux-aws | Ubuntu | upstream | * |
Linux-aws-5.0 | Ubuntu | esm-infra/bionic | * |
Linux-aws-5.0 | Ubuntu | upstream | * |
Linux-aws-5.11 | Ubuntu | focal | * |
Linux-aws-5.11 | Ubuntu | upstream | * |
Linux-aws-5.13 | Ubuntu | focal | * |
Linux-aws-5.13 | Ubuntu | upstream | * |
Linux-aws-5.15 | Ubuntu | upstream | * |
Linux-aws-5.19 | Ubuntu | jammy | * |
Linux-aws-5.19 | Ubuntu | upstream | * |
Linux-aws-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-aws-5.3 | Ubuntu | upstream | * |
Linux-aws-5.4 | Ubuntu | upstream | * |
Linux-aws-5.8 | Ubuntu | focal | * |
Linux-aws-5.8 | Ubuntu | upstream | * |
Linux-aws-6.2 | Ubuntu | jammy | * |
Linux-aws-6.2 | Ubuntu | upstream | * |
Linux-aws-6.5 | Ubuntu | upstream | * |
Linux-aws-fips | Ubuntu | upstream | * |
Linux-aws-hwe | Ubuntu | upstream | * |
Linux-azure | Ubuntu | esm-infra/bionic | * |
Linux-azure | Ubuntu | upstream | * |
Linux-azure-4.15 | Ubuntu | upstream | * |
Linux-azure-5.11 | Ubuntu | focal | * |
Linux-azure-5.11 | Ubuntu | upstream | * |
Linux-azure-5.13 | Ubuntu | focal | * |
Linux-azure-5.13 | Ubuntu | upstream | * |
Linux-azure-5.15 | Ubuntu | upstream | * |
Linux-azure-5.19 | Ubuntu | jammy | * |
Linux-azure-5.19 | Ubuntu | upstream | * |
Linux-azure-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-azure-5.3 | Ubuntu | upstream | * |
Linux-azure-5.4 | Ubuntu | upstream | * |
Linux-azure-5.8 | Ubuntu | focal | * |
Linux-azure-5.8 | Ubuntu | upstream | * |
Linux-azure-6.2 | Ubuntu | jammy | * |
Linux-azure-6.2 | Ubuntu | upstream | * |
Linux-azure-6.5 | Ubuntu | upstream | * |
Linux-azure-edge | Ubuntu | esm-infra/bionic | * |
Linux-azure-edge | Ubuntu | upstream | * |
Linux-azure-fde | Ubuntu | focal | * |
Linux-azure-fde | Ubuntu | upstream | * |
Linux-azure-fde-5.15 | Ubuntu | upstream | * |
Linux-azure-fde-5.19 | Ubuntu | jammy | * |
Linux-azure-fde-5.19 | Ubuntu | upstream | * |
Linux-azure-fde-6.2 | Ubuntu | jammy | * |
Linux-azure-fde-6.2 | Ubuntu | upstream | * |
Linux-azure-fips | Ubuntu | upstream | * |
Linux-bluefield | Ubuntu | upstream | * |
Linux-fips | Ubuntu | upstream | * |
Linux-gcp | Ubuntu | esm-infra/bionic | * |
Linux-gcp | Ubuntu | upstream | * |
Linux-gcp-4.15 | Ubuntu | upstream | * |
Linux-gcp-5.11 | Ubuntu | focal | * |
Linux-gcp-5.11 | Ubuntu | upstream | * |
Linux-gcp-5.13 | Ubuntu | focal | * |
Linux-gcp-5.13 | Ubuntu | upstream | * |
Linux-gcp-5.15 | Ubuntu | upstream | * |
Linux-gcp-5.19 | Ubuntu | jammy | * |
Linux-gcp-5.19 | Ubuntu | upstream | * |
Linux-gcp-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-gcp-5.3 | Ubuntu | upstream | * |
Linux-gcp-5.4 | Ubuntu | upstream | * |
Linux-gcp-5.8 | Ubuntu | focal | * |
Linux-gcp-5.8 | Ubuntu | upstream | * |
Linux-gcp-6.2 | Ubuntu | jammy | * |
Linux-gcp-6.2 | Ubuntu | upstream | * |
Linux-gcp-6.5 | Ubuntu | upstream | * |
Linux-gcp-fips | Ubuntu | upstream | * |
Linux-gke | Ubuntu | focal | * |
Linux-gke | Ubuntu | upstream | * |
Linux-gke-4.15 | Ubuntu | esm-infra/bionic | * |
Linux-gke-4.15 | Ubuntu | upstream | * |
Linux-gke-5.15 | Ubuntu | focal | * |
Linux-gke-5.15 | Ubuntu | upstream | * |
Linux-gke-5.4 | Ubuntu | esm-infra/bionic | * |
Linux-gke-5.4 | Ubuntu | upstream | * |
Linux-gkeop | Ubuntu | upstream | * |
Linux-gkeop-5.15 | Ubuntu | upstream | * |
Linux-gkeop-5.4 | Ubuntu | esm-infra/bionic | * |
Linux-gkeop-5.4 | Ubuntu | upstream | * |
Linux-hwe | Ubuntu | esm-infra/bionic | * |
Linux-hwe | Ubuntu | upstream | * |
Linux-hwe-5.11 | Ubuntu | focal | * |
Linux-hwe-5.11 | Ubuntu | upstream | * |
Linux-hwe-5.13 | Ubuntu | focal | * |
Linux-hwe-5.13 | Ubuntu | upstream | * |
Linux-hwe-5.15 | Ubuntu | upstream | * |
Linux-hwe-5.19 | Ubuntu | jammy | * |
Linux-hwe-5.19 | Ubuntu | upstream | * |
Linux-hwe-5.4 | Ubuntu | upstream | * |
Linux-hwe-5.8 | Ubuntu | focal | * |
Linux-hwe-5.8 | Ubuntu | upstream | * |
Linux-hwe-6.2 | Ubuntu | jammy | * |
Linux-hwe-6.2 | Ubuntu | upstream | * |
Linux-hwe-6.5 | Ubuntu | upstream | * |
Linux-hwe-edge | Ubuntu | esm-infra/bionic | * |
Linux-hwe-edge | Ubuntu | esm-infra/xenial | * |
Linux-hwe-edge | Ubuntu | upstream | * |
Linux-ibm | Ubuntu | mantic | * |
Linux-ibm | Ubuntu | upstream | * |
Linux-ibm-5.15 | Ubuntu | upstream | * |
Linux-ibm-5.4 | Ubuntu | upstream | * |
Linux-intel | Ubuntu | upstream | * |
Linux-intel-5.13 | Ubuntu | focal | * |
Linux-intel-5.13 | Ubuntu | upstream | * |
Linux-intel-iotg | Ubuntu | upstream | * |
Linux-intel-iotg-5.15 | Ubuntu | upstream | * |
Linux-iot | Ubuntu | upstream | * |
Linux-kvm | Ubuntu | upstream | * |
Linux-laptop | Ubuntu | upstream | * |
Linux-lowlatency | Ubuntu | upstream | * |
Linux-lowlatency-hwe-5.15 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-5.19 | Ubuntu | jammy | * |
Linux-lowlatency-hwe-5.19 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-6.2 | Ubuntu | jammy | * |
Linux-lowlatency-hwe-6.2 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-6.5 | Ubuntu | upstream | * |
Linux-lts-xenial | Ubuntu | upstream | * |
Linux-nvidia | Ubuntu | upstream | * |
Linux-nvidia-6.2 | Ubuntu | jammy | * |
Linux-nvidia-6.2 | Ubuntu | upstream | * |
Linux-nvidia-6.5 | Ubuntu | upstream | * |
Linux-oem | Ubuntu | esm-infra/bionic | * |
Linux-oem | Ubuntu | upstream | * |
Linux-oem-5.10 | Ubuntu | focal | * |
Linux-oem-5.10 | Ubuntu | upstream | * |
Linux-oem-5.13 | Ubuntu | focal | * |
Linux-oem-5.13 | Ubuntu | upstream | * |
Linux-oem-5.14 | Ubuntu | focal | * |
Linux-oem-5.14 | Ubuntu | upstream | * |
Linux-oem-5.17 | Ubuntu | jammy | * |
Linux-oem-5.17 | Ubuntu | upstream | * |
Linux-oem-5.6 | Ubuntu | focal | * |
Linux-oem-5.6 | Ubuntu | upstream | * |
Linux-oem-6.0 | Ubuntu | jammy | * |
Linux-oem-6.0 | Ubuntu | upstream | * |
Linux-oem-6.1 | Ubuntu | jammy | * |
Linux-oem-6.1 | Ubuntu | upstream | * |
Linux-oem-6.5 | Ubuntu | upstream | * |
Linux-oem-6.8 | Ubuntu | upstream | * |
Linux-oracle | Ubuntu | upstream | * |
Linux-oracle-5.0 | Ubuntu | esm-infra/bionic | * |
Linux-oracle-5.0 | Ubuntu | upstream | * |
Linux-oracle-5.11 | Ubuntu | focal | * |
Linux-oracle-5.11 | Ubuntu | upstream | * |
Linux-oracle-5.13 | Ubuntu | focal | * |
Linux-oracle-5.13 | Ubuntu | upstream | * |
Linux-oracle-5.15 | Ubuntu | upstream | * |
Linux-oracle-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-oracle-5.3 | Ubuntu | upstream | * |
Linux-oracle-5.4 | Ubuntu | upstream | * |
Linux-oracle-5.8 | Ubuntu | focal | * |
Linux-oracle-5.8 | Ubuntu | upstream | * |
Linux-oracle-6.5 | Ubuntu | upstream | * |
Linux-raspi | Ubuntu | upstream | * |
Linux-raspi-5.4 | Ubuntu | upstream | * |
Linux-raspi2 | Ubuntu | focal | * |
Linux-raspi2 | Ubuntu | upstream | * |
Linux-riscv | Ubuntu | focal | * |
Linux-riscv | Ubuntu | jammy | * |
Linux-riscv | Ubuntu | upstream | * |
Linux-riscv-5.11 | Ubuntu | focal | * |
Linux-riscv-5.11 | Ubuntu | upstream | * |
Linux-riscv-5.15 | Ubuntu | upstream | * |
Linux-riscv-5.19 | Ubuntu | jammy | * |
Linux-riscv-5.19 | Ubuntu | upstream | * |
Linux-riscv-5.8 | Ubuntu | focal | * |
Linux-riscv-5.8 | Ubuntu | upstream | * |
Linux-riscv-6.5 | Ubuntu | upstream | * |
Linux-starfive | Ubuntu | upstream | * |
Linux-starfive-5.19 | Ubuntu | jammy | * |
Linux-starfive-5.19 | Ubuntu | upstream | * |
Linux-starfive-6.2 | Ubuntu | jammy | * |
Linux-starfive-6.2 | Ubuntu | upstream | * |
Linux-starfive-6.5 | Ubuntu | upstream | * |
Linux-xilinx-zynqmp | Ubuntu | upstream | * |