CVE-2026-89580
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
A vulnerability was fixed in the Linux kernel's __bpf_get_stack function. The per-CPU perf_callchain_entry buffer returned by get_perf_callchain() is not protected against reuse after being returned, so a preemptible BPF program can be scheduled out between obtaining the buffer and copying it, allowing another task on the same CPU to overwrite trace->nr with a larger value. This causes copy_len to be computed from the inflated value and leads to an out-of-bounds write in memcpy() and in the build_id path.
Risk Assessment
The vulnerability allows kernel memory corruption (out-of-bounds write) by a local BPF program, potentially leading to system crash or privilege escalation. It affects kernels with CONFIG_PREEMPT enabled and BPF programs running in a preemptible context.
Recommendation
Update the Linux kernel to a version containing the fix that disables preemption around obtaining and copying the callchain entry in __bpf_get_stack. If updating is not possible, restrict the ability to load BPF programs to trusted users.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: bpf: Disable preemption in __bpf_get_stack get_perf_callchain() returns a per-CPU perf_callchain_entry buffer and releases its recursion slot via put_callchain_entry() before returning, so nothing keeps the entry reserved while __bpf_get_stack() consumes it below. A preemptible BPF program (e.g. a non-sleepable raw tracepoint program on a PREEMPT kernel, which runs under migrate_disable() but not preempt_disable()) can be scheduled out between obtaining the entry and the copy. Another task scheduled on the same CPU then reuses the same per-CPU buffer and overwrites trace->nr with a larger value. copy_len is then computed from the inflated trace->nr and can exceed the caller's buffer, causing an out-of-bounds write in the memcpy() and in the build_id path. The rcu_read_lock() taken here alone does not prevent this. It is only taken on the may_fault path, and under CONFIG_PREEMPT_RCU it does not disable preemption; it merely keeps perf's callchain buffer array alive (freed via call_rcu()) and does nothing to stop another task from reusing the entry. Disable preemption around obtaining the callchain entry and copying it into the caller's buffer, so the entry cannot be reused underneath us and trace->nr stays bounded by max_depth. Build ID resolution may fault and is therefore deferred until after preemption is re-enabled; by then the instruction pointers have already been copied into buf, so it operates only on that private copy. Note, preempt_disable() also subsumes the buffer-lifetime guarantee the rcu_read_lock() provided, since a preempt-disabled section is an RCU read-side critical section for the callchain buffers' call_rcu() reclaim. [ changed Fixes: commit ]
Vulnerability data from NVD (NIST) · CISA KEV · EPSS