Low [CVE-2026-64075] Fix unregister_fprobe to wait for RCU grace period
This low-severity Red Hat Linux advisory covers CVE-2026-64075.
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Summary
In the Linux kernel, the following vulnerability has been resolved: fprobe: Fix unregister_fprobe() to wait for RCU grace period Commit 4346ba1604093 ("fprobe: Rewrite fprobe on function-graph tracer") changed fprobe to register struct fprobe to an rcu-hlist, but it forgot to wait for RCU GP.
Thus there can be use-after-free if the fprobe is released right after unregistering. This can be happened on fprobe event and sample module code.
To fix this issue, add synchronize_rcu() in unregister_fprobe(). Note that BPF is OK because fprobe is used as a part of bpf_kprobe_multi_link.
This unregisters its fprobe in bpf_kprobe_multi_link_release() and it is deallocated via bpf_kprobe_multi_link_dealloc(), which is invoked from bpf_link_defer_dealloc_rcu_gp() RCU callback. For BPF, this also introduced unregister_fprobe_async() which does NOT wait for RCU grace priod.
The 'unregister_fprobe()' function did not properly wait for the RCU (Read-Copy-Update) grace period, which is a synchronization mechanism. This oversight could lead to a use-after-free vulnerability, where memory is deallocated while still being accessed.
Such a flaw can result in system instability, leading to a denial of service, and in some cases, could be exploited by a local attacker to achieve arbitrary code execution. Red Hat severity: Low.
Weakness: CWE-825.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · medium-confidence parse· fetched 7 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 7 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 7 days ago·verify at source
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