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bpf: Forget ranges when refining tnum after JSET

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2025-39748

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2025-39748

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
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Prerequisites
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Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "22191359f8454b0be082c3b126f86bcbea0f1318",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "c29dd8336236a4deb75596b52d2dd16ccc4a380d",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "591c788d16046edb0220800bf1819554af5853ce",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "0643aa2468192a4d81326e8e76543854870b1ee2",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "f01e06930444cab289a8783017af9b64255bd103",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "2fd0c26bacd90ef26522bd3169000a4715bf151f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "80a6b11862a7cfdf691e8f9faee89cfea219f098",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "960ea056561a08e2b837b2f02d22c53226414a84",
        "lessThan": "6279846b9b2532e1b04559ef8bd0dec049f29383",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "kernel/bpf/verifier.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "5.0"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "5.0",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.253",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.203",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.167",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.130",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.43",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.15.11",
        "versionType": "semver",
        "lessThanOrEqual": "6.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.16.2",
        "versionType": "semver",
        "lessThanOrEqual": "6.16.*"
      },
      {
        "status": "unaffected",
        "version": "6.17",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "kernel/bpf/verifier.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2025-39748

Source reference: /cveMetadata/cveId

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Event
#27061 · Revision 1
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