Description
In the Linux kernel, the following vulnerability has been resolved:
fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()
unregister_fprobe() and unregister_fprobe_async() (used by BPF
kprobe-multi) rely on standard RCU grace periods (synchronize_rcu()
and call_rcu()) to wait until in-flight fprobe handlers complete before
freeing the fprobe.
However, if an fprobe handler executes while RCU is not watching (such
as in the idle loop or nohz_full extended quiescent states), standard
RCU does not track preemption-disabled sections. Consequently,
synchronize_rcu() does not wait for those executions, which can lead
to a use-after-free if the fprobe is freed immediately after
unregistration. Ensure handlers exit early when !rcu_is_watching().
Furthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously
used guard(rcu)() and rcu_read_lock(), which invoke lockdep on every
hit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep
recursion if probed functions interact with lockdep.
Since rhltable_lookup() and rhl_for_each_entry_rcu() use
rcu_dereference_all_check() (which checks rcu_read_lock_any_held()),
holding preemption disabled via rcu_read_lock_sched_notrace() is fully
valid and sufficient so long as rcu_is_watching() is true.
Define and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(),
fprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path
rcu_read_lock() and lockdep overhead while guaranteeing safe grace
period synchronization.
fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching()
unregister_fprobe() and unregister_fprobe_async() (used by BPF
kprobe-multi) rely on standard RCU grace periods (synchronize_rcu()
and call_rcu()) to wait until in-flight fprobe handlers complete before
freeing the fprobe.
However, if an fprobe handler executes while RCU is not watching (such
as in the idle loop or nohz_full extended quiescent states), standard
RCU does not track preemption-disabled sections. Consequently,
synchronize_rcu() does not wait for those executions, which can lead
to a use-after-free if the fprobe is freed immediately after
unregistration. Ensure handlers exit early when !rcu_is_watching().
Furthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously
used guard(rcu)() and rcu_read_lock(), which invoke lockdep on every
hit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep
recursion if probed functions interact with lockdep.
Since rhltable_lookup() and rhl_for_each_entry_rcu() use
rcu_dereference_all_check() (which checks rcu_read_lock_any_held()),
holding preemption disabled via rcu_read_lock_sched_notrace() is fully
valid and sufficient so long as rcu_is_watching() is true.
Define and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(),
fprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path
rcu_read_lock() and lockdep overhead while guaranteeing safe grace
period synchronization.
Published:
2026-10-18
Score:
n/a
EPSS:
n/a
KEV:
No
Impact:
n/a
Action:
n/a
Analysis
Analysis and contextual insights are available on OpenCVE Cloud.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||||||||
| Linux | Linux | affected |
|
No data.
No data.
No data available yet.
Remediation
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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Advisories
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References
History
Sun, 18 Oct 2026 16:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching() unregister_fprobe() and unregister_fprobe_async() (used by BPF kprobe-multi) rely on standard RCU grace periods (synchronize_rcu() and call_rcu()) to wait until in-flight fprobe handlers complete before freeing the fprobe. However, if an fprobe handler executes while RCU is not watching (such as in the idle loop or nohz_full extended quiescent states), standard RCU does not track preemption-disabled sections. Consequently, synchronize_rcu() does not wait for those executions, which can lead to a use-after-free if the fprobe is freed immediately after unregistration. Ensure handlers exit early when !rcu_is_watching(). Furthermore, fprobe_fgraph_entry() and fprobe_ftrace_entry() previously used guard(rcu)() and rcu_read_lock(), which invoke lockdep on every hit under CONFIG_PROVE_LOCKING. This adds overhead and can cause lockdep recursion if probed functions interact with lockdep. Since rhltable_lookup() and rhl_for_each_entry_rcu() use rcu_dereference_all_check() (which checks rcu_read_lock_any_held()), holding preemption disabled via rcu_read_lock_sched_notrace() is fully valid and sufficient so long as rcu_is_watching() is true. Define and use guard(rcu_sched_notrace)() across fprobe_ftrace_entry(), fprobe_fgraph_entry(), and fprobe_return(). This eliminates fast-path rcu_read_lock() and lockdep overhead while guaranteeing safe grace period synchronization. | |
| Title | fprobe: Use guard(rcu_sched_notrace) and check rcu_is_watching() | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-10-18T15:51:22.271Z
Reserved: 2026-09-25T10:25:14.376Z
Link: CVE-2026-98861
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-18T16:17:40.573
Modified: 2026-10-18T16:17:40.573
Link: CVE-2026-98861
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.