CVE-2026-90317bpf: Invalidate RCU pointers after final spin unlock

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: Invalidate RCU pointers after final spin unlock In a sleepable BPF program, a spin lock can provide the only RCU protection for a kptr. The final bpf_spin_unlock() ends that protection, but the verifier leaves the pointer valid. Another CPU can then free the object before the pointer is used. A capability-limited runtime PoC triggered a task_struct use-after-free in __bpf_get_task_stack(). Record whether the program is in an RCU-protected context before releasing the lock. Invalidate RCU-protected pointers only when the unlock leaves the final such context. This preserves valid pointers in non-sleepable programs and inside an explicit RCU read-side section.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/f81972b235f3ebfa40bdce8bcfee3f242fb24065
• https://git.kernel.org/stable/c/7ae71629357d0a6d0bdadb929c7b296d5b7e61c2
• https://git.kernel.org/stable/c/180c7000712db77063b3a26f4c97e7dd9038f449