In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix infinite loop in pcpu_freelist push with one possible CPU
__pcpu_freelist_push() can loop forever when only one CPU is possible
and an NMI re-enters pcpu_freelist_push() while the interrupted context
holds that CPU's freelist lock.
After the current-CPU fast path fails, the fallback loop walks
cpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or
when an SMP kernel is limited to one possible CPU with nr_cpus=1 or
possible_cpus=1, there are no other possible CPUs to examine. The loop
therefore makes no lock acquisition attempt and can never make progress.
The following stack was observed on a UP system:
NMI context:
pcpu_freelist_push
free_htab_elem
htab_map_delete_elem
[perf-event BPF program]
__perf_event_overflow
perf_event_nmi_handler
exc_nmi
Interrupted context:
__pcpu_freelist_push
pcpu_freelist_push
free_htab_elem
htab_map_delete_elem
[raw_tp/sys_enter BPF program]
__bpf_trace_sys_enter
do_syscall_64
raw_res_spin_lock() detects the same-CPU recursive acquisition and
returns -EDEADLK, but the subsequent fallback loop has no candidate head
on a system with one possible CPU.
Restore the extra fallback head that existed before the rqspinlock
conversion. Keep the current-CPU fast path, then try the other possible
CPUs and finally the extra head. The additional head lets a push, which
cannot fail without losing a preallocated element, make progress when the
only per-CPU head is held by the interrupted context.
Also check the extra head from the pop path so that nodes placed there
can be reused.
bpf: Fix infinite loop in pcpu_freelist push with one possible CPU
__pcpu_freelist_push() can loop forever when only one CPU is possible
and an NMI re-enters pcpu_freelist_push() while the interrupted context
holds that CPU's freelist lock.
After the current-CPU fast path fails, the fallback loop walks
cpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or
when an SMP kernel is limited to one possible CPU with nr_cpus=1 or
possible_cpus=1, there are no other possible CPUs to examine. The loop
therefore makes no lock acquisition attempt and can never make progress.
The following stack was observed on a UP system:
NMI context:
pcpu_freelist_push
free_htab_elem
htab_map_delete_elem
[perf-event BPF program]
__perf_event_overflow
perf_event_nmi_handler
exc_nmi
Interrupted context:
__pcpu_freelist_push
pcpu_freelist_push
free_htab_elem
htab_map_delete_elem
[raw_tp/sys_enter BPF program]
__bpf_trace_sys_enter
do_syscall_64
raw_res_spin_lock() detects the same-CPU recursive acquisition and
returns -EDEADLK, but the subsequent fallback loop has no candidate head
on a system with one possible CPU.
Restore the extra fallback head that existed before the rqspinlock
conversion. Keep the current-CPU fast path, then try the other possible
CPUs and finally the extra head. The additional head lets a push, which
cannot fail without losing a preallocated element, make progress when the
only per-CPU head is held by the interrupted context.
Also check the extra head from the pop path so that nodes placed there
can be reused.
Metrics
Affected Vendors & Products
Advisories
No advisories yet.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Wed, 16 Sep 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: Fix infinite loop in pcpu_freelist push with one possible CPU __pcpu_freelist_push() can loop forever when only one CPU is possible and an NMI re-enters pcpu_freelist_push() while the interrupted context holds that CPU's freelist lock. After the current-CPU fast path fails, the fallback loop walks cpu_possible_mask while skipping the current CPU. With CONFIG_SMP=n, or when an SMP kernel is limited to one possible CPU with nr_cpus=1 or possible_cpus=1, there are no other possible CPUs to examine. The loop therefore makes no lock acquisition attempt and can never make progress. The following stack was observed on a UP system: NMI context: pcpu_freelist_push free_htab_elem htab_map_delete_elem [perf-event BPF program] __perf_event_overflow perf_event_nmi_handler exc_nmi Interrupted context: __pcpu_freelist_push pcpu_freelist_push free_htab_elem htab_map_delete_elem [raw_tp/sys_enter BPF program] __bpf_trace_sys_enter do_syscall_64 raw_res_spin_lock() detects the same-CPU recursive acquisition and returns -EDEADLK, but the subsequent fallback loop has no candidate head on a system with one possible CPU. Restore the extra fallback head that existed before the rqspinlock conversion. Keep the current-CPU fast path, then try the other possible CPUs and finally the extra head. The additional head lets a push, which cannot fail without losing a preallocated element, make progress when the only per-CPU head is held by the interrupted context. Also check the extra head from the pop path so that nodes placed there can be reused. | |
| Title | bpf: Fix infinite loop in pcpu_freelist push with one possible CPU | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-16T10:33:05.097Z
Reserved: 2026-09-11T19:38:34.780Z
Link: CVE-2026-89991
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-16T11:17:10.240
Modified: 2026-09-16T11:17:10.240
Link: CVE-2026-89991
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.