bpf: Fix objects stuck in free_by_rcu_ttrace
do_call_rcu_ttrace() returns early when call_rcu_ttrace_in_progress is set
and leaves the objects in free_by_rcu_ttrace. __free_rcu() frees
waiting_for_gp_ttrace only and clears the flag. Hence the objects that
free_bulk() or __free_by_rcu() added while RCU tasks trace GP was in flight
stay in free_by_rcu_ttrace until free_bulk() or alloc_bulk() is called for
the same bpf_mem_cache again, which may never happen. The number of such
objects is not bounded.
Turn call_rcu_ttrace_in_progress into three states:
0 - idle
1 - __free_rcu() is queued
2 - __free_rcu() is queued and free_by_rcu_ttrace got more objects since
do_call_rcu_ttrace() sets 2. __free_rcu() does cmpxchg(1 -> 0) and starts
the next GP when it fails. It cannot clear the flag first and check
free_by_rcu_ttrace later, since bpf_mem_alloc_destroy() frees bpf_mem_cache
without waiting for RCU callbacks when the flag is zero.
Now __free_rcu() queues itself, so the one that didn't see 'draining' may
do call_rcu_tasks_trace() after rcu_barrier_tasks_trace() in
free_mem_alloc(). Queue it under rcu_read_lock() and do synchronize_rcu()
before the barriers. Calling rcu_barrier_tasks_trace() twice works too, but
creating and destroying hash maps in a loop on many cpus slows down to one
free_mem_alloc() per GP and kworkers pile up.
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.
No solution or workaround provided in the CVE record.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
Sign in to view the affected projects.
No advisories yet.
Sun, 18 Oct 2026 16:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: Fix objects stuck in free_by_rcu_ttrace do_call_rcu_ttrace() returns early when call_rcu_ttrace_in_progress is set and leaves the objects in free_by_rcu_ttrace. __free_rcu() frees waiting_for_gp_ttrace only and clears the flag. Hence the objects that free_bulk() or __free_by_rcu() added while RCU tasks trace GP was in flight stay in free_by_rcu_ttrace until free_bulk() or alloc_bulk() is called for the same bpf_mem_cache again, which may never happen. The number of such objects is not bounded. Turn call_rcu_ttrace_in_progress into three states: 0 - idle 1 - __free_rcu() is queued 2 - __free_rcu() is queued and free_by_rcu_ttrace got more objects since do_call_rcu_ttrace() sets 2. __free_rcu() does cmpxchg(1 -> 0) and starts the next GP when it fails. It cannot clear the flag first and check free_by_rcu_ttrace later, since bpf_mem_alloc_destroy() frees bpf_mem_cache without waiting for RCU callbacks when the flag is zero. Now __free_rcu() queues itself, so the one that didn't see 'draining' may do call_rcu_tasks_trace() after rcu_barrier_tasks_trace() in free_mem_alloc(). Queue it under rcu_read_lock() and do synchronize_rcu() before the barriers. Calling rcu_barrier_tasks_trace() twice works too, but creating and destroying hash maps in a loop on many cpus slows down to one free_mem_alloc() per GP and kworkers pile up. | |
| Title | bpf: Fix objects stuck in free_by_rcu_ttrace | |
| 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: 2026-10-18T15:48:25.665Z
Reserved: 2026-09-25T10:25:14.370Z
Link: CVE-2026-98789
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-10-18T16:17:32.887
Modified: 2026-10-18T16:17:32.887
Link: CVE-2026-98789
Redhat
No data.
OpenCVE Enrichment
No data.
No weakness.