Advisory [CVE-2026-64075] Fix unregister_fprobe to wait for RCU grace period
This security 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: not rated.
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 is not a statement that 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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