GHSA-9W72-PQ5V-MQV8
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-13 09:32In 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 ]
{
"affected": [],
"aliases": [
"CVE-2026-89580"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:42Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Disable preemption in __bpf_get_stack\n\nget_perf_callchain() returns a per-CPU perf_callchain_entry buffer and\nreleases its recursion slot via put_callchain_entry() before returning,\nso nothing keeps the entry reserved while __bpf_get_stack() consumes\nit below.\n\nA preemptible BPF program (e.g. a non-sleepable raw tracepoint program\non a PREEMPT kernel, which runs under migrate_disable() but not\npreempt_disable()) can be scheduled out between obtaining the entry\nand the copy. Another task scheduled on the same CPU then reuses the\nsame per-CPU buffer and overwrites trace-\u003enr with a larger value.\ncopy_len is then computed from the inflated trace-\u003enr and can exceed\nthe caller\u0027s buffer, causing an out-of-bounds write in the memcpy()\nand in the build_id path.\n\nThe rcu_read_lock() taken here alone does not prevent this. It is\nonly taken on the may_fault path, and under CONFIG_PREEMPT_RCU it does\nnot disable preemption; it merely keeps perf\u0027s callchain buffer array\nalive (freed via call_rcu()) and does nothing to stop another task\nfrom reusing the entry.\n\nDisable preemption around obtaining the callchain entry and copying\nit into the caller\u0027s buffer, so the entry cannot be reused underneath\nus and trace-\u003enr stays bounded by max_depth. Build ID resolution may\nfault and is therefore deferred until after preemption is re-enabled;\nby then the instruction pointers have already been copied into buf,\nso it operates only on that private copy. Note, preempt_disable() also\nsubsumes the buffer-lifetime guarantee the rcu_read_lock() provided,\nsince a preempt-disabled section is an RCU read-side critical section\nfor the callchain buffers\u0027 call_rcu() reclaim.\n\n\n[ changed Fixes: commit ]",
"id": "GHSA-9w72-pq5v-mqv8",
"modified": "2026-09-13T09:32:19Z",
"published": "2026-09-11T21:31:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89580"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8c5ba022f2085ea42d011497a6e92e527d123b9b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9a23747909fcae707990c8466c381a0e7acfaa4e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b1a47b2708d4e95dbd23aee2ec83752190897b3f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dbfecc8a6631c0d3626c14ba1f1a485a4498445a"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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