ghsa-v488-2vhj-rwrj
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
bpf: Forget ranges when refining tnum after JSET
Syzbot reported a kernel warning due to a range invariant violation on the following BPF program.
0: call bpf_get_netns_cookie 1: if r0 == 0 goto 2: if r0 & Oxffffffff goto
The issue is on the path where we fall through both jumps.
That path is unreachable at runtime: after insn 1, we know r0 != 0, but with the sign extension on the jset, we would only fallthrough insn 2 if r0 == 0. Unfortunately, is_branch_taken() isn't currently able to figure this out, so the verifier walks all branches. The verifier then refines the register bounds using the second condition and we end up with inconsistent bounds on this unreachable path:
1: if r0 == 0 goto r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff) 2: if r0 & 0xffffffff goto r0 before reg_bounds_sync: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0) r0 after reg_bounds_sync: u64=[0x1, 0] var_off=(0, 0)
Improving the range refinement for JSET to cover all cases is tricky. We also don't expect many users to rely on JSET given LLVM doesn't generate those instructions. So instead of improving the range refinement for JSETs, Eduard suggested we forget the ranges whenever we're narrowing tnums after a JSET. This patch implements that approach.
{
"affected": [],
"aliases": [
"CVE-2025-39748"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-11T17:15:38Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Forget ranges when refining tnum after JSET\n\nSyzbot reported a kernel warning due to a range invariant violation on\nthe following BPF program.\n\n 0: call bpf_get_netns_cookie\n 1: if r0 == 0 goto \u003cexit\u003e\n 2: if r0 \u0026 Oxffffffff goto \u003cexit\u003e\n\nThe issue is on the path where we fall through both jumps.\n\nThat path is unreachable at runtime: after insn 1, we know r0 != 0, but\nwith the sign extension on the jset, we would only fallthrough insn 2\nif r0 == 0. Unfortunately, is_branch_taken() isn\u0027t currently able to\nfigure this out, so the verifier walks all branches. The verifier then\nrefines the register bounds using the second condition and we end\nup with inconsistent bounds on this unreachable path:\n\n 1: if r0 == 0 goto \u003cexit\u003e\n r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff)\n 2: if r0 \u0026 0xffffffff goto \u003cexit\u003e\n r0 before reg_bounds_sync: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0)\n r0 after reg_bounds_sync: u64=[0x1, 0] var_off=(0, 0)\n\nImproving the range refinement for JSET to cover all cases is tricky. We\nalso don\u0027t expect many users to rely on JSET given LLVM doesn\u0027t generate\nthose instructions. So instead of improving the range refinement for\nJSETs, Eduard suggested we forget the ranges whenever we\u0027re narrowing\ntnums after a JSET. This patch implements that approach.",
"id": "GHSA-v488-2vhj-rwrj",
"modified": "2025-09-11T18:35:51Z",
"published": "2025-09-11T18:35:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39748"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2fd0c26bacd90ef26522bd3169000a4715bf151f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6279846b9b2532e1b04559ef8bd0dec049f29383"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/80a6b11862a7cfdf691e8f9faee89cfea219f098"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f01e06930444cab289a8783017af9b64255bd103"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
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