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CVE-2025-39748

bpf: Forget ranges when refining tnum after JSET

MEDIUM 5.5

At a glance

Source
NVD
EPSS
EPSS 0.17 % · percentile 7 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Modified

Description

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 <exit> 2: if r0 & Oxffffffff goto <exit> 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 <exit> r0: u64=[0x1, 0xffffffffffffffff] var_off=(0, 0xffffffffffffffff) 2: if r0 & 0xffffffff goto <exit> 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.

References

Scores

VersionScoreVectorScored by
CVSS 3.1MEDIUM 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HNVD · nvd@nist.gov (Primary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected 960ea056561a08e2b837b2f02d22c53226414a84 < 22191359f8454b0be082c3b126f86bcbea0f1318 ; affected 960ea056561a08e2b837b2f02d22c53226414a84 < c29dd8336236a4deb75596b52d2dd16ccc4a380d ; affected 960ea056561a08e2b837b2f02d22c53226414a84 < 591c788d16046edb0220800bf1819554af5853ce ; affected 960ea056561a08e2b837b2f02d22c53226414a84 < 0643aa2468192a4d81326e8e76543854870b1ee2 ; affected 960ea056561a08e2b837b2f02d22c53226414a84 < f01e06930444cab289a8783017af9b64255bd103 ; affected 960ea056561a08e2b837b2f02d22c53226414a84 < 2fd0c26bacd90ef26522bd3169000a4715bf151f
Linux · Linuxaffected 5.0 ; unaffected 0 < 5.0 ; unaffected 5.10.253 ≤ 5.10.* ; unaffected 5.15.203 ≤ 5.15.* ; unaffected 6.1.167 ≤ 6.1.* ; unaffected 6.6.130 ≤ 6.6.*

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD