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 powerpc's arch_cpu_idle_dead() decrements the idle task's
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: Don't touch the idle
task's preempt_count during hotplug") and commit f1a0a376ca0c ("sched/core:
Initialize the idle task with preemption disabled"), that justification no
longer holds.
The idle task isn't 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.
Metrics
Affected Vendors & Products
References
History
Wed, 13 Nov 2024 02:30:00 +0000
Type | Values Removed | Values Added |
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First Time appeared |
Redhat
Redhat enterprise Linux |
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CPEs | cpe:/a:redhat:enterprise_linux:9 cpe:/o:redhat:enterprise_linux:9 |
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Vendors & Products |
Redhat
Redhat enterprise Linux |
Mon, 04 Nov 2024 12:15:00 +0000
Type | Values Removed | Values Added |
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Metrics |
ssvc
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MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2024-05-22T06:19:44.040Z
Updated: 2024-12-19T07:42:37.372Z
Reserved: 2024-05-21T14:58:30.833Z
Link: CVE-2021-47454
Vulnrichment
Updated: 2024-08-04T05:39:59.627Z
NVD
Status : Awaiting Analysis
Published: 2024-05-22T07:15:10.453
Modified: 2024-11-21T06:36:10.763
Link: CVE-2021-47454
Redhat