GHSA-W2C5-6C3V-2HF7
Vulnerability from github – Published: 2026-09-16 12:30 – Updated: 2026-09-16 15:31In the Linux kernel, the following vulnerability has been resolved:
LoongArch: Avoid preempt count underflow without probe
LoongArch uses break 11 for the breakpoint placed after an instruction that Kprobes executes out of line. Since userspace can issue the same break instruction, do_bp() can reach kprobe_singlestep_handler() when there is no current probe.
The handler actually returns false in this case, but it first calls preempt_enable_no_resched(). The corresponding preempt_disable() is done by kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run here. As a result, an ordinary userspace breakpoint (code 11) underflows the current task's preempt count.
This also makes in_interrupt() return true until the task schedules. One visible consequence is the socket cgroup attribution: cgroup_sk_alloc() treats the allocation as interrupt context and assigns the socket to the root cgroup. A socket opened from the SIGTRAP handler can then avoid a BPF_CGROUP_INET_SOCK_CREATE policy attached to the task's own cgroup.
Return as soon as kprobe_running() reports no active probe.
The same check has appeared in [PATCH v10 2/4] of the original LoongArch Kprobes series, but was dropped before the feature reached mainline.
{
"affected": [],
"aliases": [
"CVE-2026-89902"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-16T11:16:59Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nLoongArch: Avoid preempt count underflow without probe\n\nLoongArch uses break 11 for the breakpoint placed after an instruction\nthat Kprobes executes out of line. Since userspace can issue the same\nbreak instruction, do_bp() can reach kprobe_singlestep_handler() when\nthere is no current probe.\n\nThe handler actually returns false in this case, but it first calls\npreempt_enable_no_resched(). The corresponding preempt_disable() is done\nby kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run\nhere. As a result, an ordinary userspace breakpoint (code 11) underflows\nthe current task\u0027s preempt count.\n\nThis also makes in_interrupt() return true until the task schedules. One\nvisible consequence is the socket cgroup attribution: cgroup_sk_alloc()\ntreats the allocation as interrupt context and assigns the socket to the\nroot cgroup. A socket opened from the SIGTRAP handler can then avoid a\nBPF_CGROUP_INET_SOCK_CREATE policy attached to the task\u0027s own cgroup.\n\nReturn as soon as kprobe_running() reports no active probe.\n\nThe same check has appeared in [PATCH v10 2/4] of the original LoongArch\nKprobes series, but was dropped before the feature reached mainline.",
"id": "GHSA-w2c5-6c3v-2hf7",
"modified": "2026-09-16T15:31:01Z",
"published": "2026-09-16T12:30:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89902"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/72ce4b24676e8b3b75376c4c559dd81c1ac52d5a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/76395109a051b53860faaec96522ef08ae9e8e27"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a1cb727fa27c2d9c7859729cd90db7bc0f46957f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c4357ebeee63cb8da1446fc936573a34e68b0f71"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ff40e597d5d98c0c45a4d09df8177202fac9520e"
}
],
"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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