Re: [PATCH] cpumask: Fix crash on updating CPU enabled mask
From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Date: 2024-08-08 08:41:15
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On Thu, 8 Aug 2024 14:08:08 +1000 Gavin Shan [off-list ref] wrote:
The CPU enabled mask instead of the CPU possible mask should be used
by set_cpu_enabled(). Otherwise, we run into crash due to write to
the read-only CPU possible mask when vCPU is hot added on ARM64.
(qemu) device_add host-arm-cpu,id=cpu1,socket-id=1
Unable to handle kernel write to read-only memory at virtual address ffff800080fa7190
:
Call trace:
register_cpu+0x1a4/0x2e8
arch_register_cpu+0x84/0xd8
acpi_processor_add+0x480/0x5b0
acpi_bus_attach+0x1c4/0x300
acpi_dev_for_one_check+0x3c/0x50
device_for_each_child+0x68/0xc8
acpi_dev_for_each_child+0x48/0x80
acpi_bus_attach+0x84/0x300
acpi_bus_scan+0x74/0x220
acpi_scan_rescan_bus+0x54/0x88
acpi_device_hotplug+0x208/0x478
acpi_hotplug_work_fn+0x2c/0x50
process_one_work+0x15c/0x3c0
worker_thread+0x2ec/0x400
kthread+0x120/0x130
ret_from_fork+0x10/0x20
Fix it by passing the CPU enabled mask instead of the CPU possible
mask to set_cpu_enabled().
Fixes: 51c4767503d5 ("Merge tag 'bitmap-6.11-rc1' of https://github.com:/norov/linux")
Signed-off-by: Gavin Shan <redacted>Thanks Gavin! We'd flagged the merge conflict but thought we'd chase it with a patch adding set_cpu_enabled() as you have it fixed below. I completely missed that Linus took a different path whilst resolving the conflict to https://lore.kernel.org/all/20240701175051.0ef5d901@canb.auug.org.au/ (local) which was what Stephen did for linux-next (which would have needed a follow up to use the new infrastructure. Anyhow, all's well that ends well. Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
quoted hunk ↗ jump to hunk
--- include/linux/cpumask.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 801a7e524113..53158de44b83 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h@@ -1037,7 +1037,7 @@ void init_cpu_online(const struct cpumask *src); assign_bit(cpumask_check(cpu), cpumask_bits(mask), (val)) #define set_cpu_possible(cpu, possible) assign_cpu((cpu), &__cpu_possible_mask, (possible)) -#define set_cpu_enabled(cpu, enabled) assign_cpu((cpu), &__cpu_possible_mask, (enabled)) +#define set_cpu_enabled(cpu, enabled) assign_cpu((cpu), &__cpu_enabled_mask, (enabled)) #define set_cpu_present(cpu, present) assign_cpu((cpu), &__cpu_present_mask, (present)) #define set_cpu_active(cpu, active) assign_cpu((cpu), &__cpu_active_mask, (active)) #define set_cpu_dying(cpu, dying) assign_cpu((cpu), &__cpu_dying_mask, (dying))