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CVE PROGRAM SOURCE RECORDUnscored

CVE-2025-39748

bpf: Forget ranges when refining tnum after JSET

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Status
Published
Published
Updated
Assigning organization
Linux

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 960ea056561a08e2b837b2f02d22c53226414a84 to < 22191359f8454b0be082c3b126f86bcbea0f1318affected
  • 960ea056561a08e2b837b2f02d22c53226414a84 to < c29dd8336236a4deb75596b52d2dd16ccc4a380daffected
  • 960ea056561a08e2b837b2f02d22c53226414a84 to < 591c788d16046edb0220800bf1819554af5853ceaffected
  • 960ea056561a08e2b837b2f02d22c53226414a84 to < 0643aa2468192a4d81326e8e76543854870b1ee2affected
  • 960ea056561a08e2b837b2f02d22c53226414a84 to < f01e06930444cab289a8783017af9b64255bd103affected
  • 960ea056561a08e2b837b2f02d22c53226414a84 to < 2fd0c26bacd90ef26522bd3169000a4715bf151faffected
  • 960ea056561a08e2b837b2f02d22c53226414a84 to < 80a6b11862a7cfdf691e8f9faee89cfea219f098affected
  • 960ea056561a08e2b837b2f02d22c53226414a84 to < 6279846b9b2532e1b04559ef8bd0dec049f29383affected

Linux Linux

Default version status: affected

  • 5.0affected
  • 0 to < 5.0unaffected
  • 5.10.253 to ≤ 5.10.*unaffected
  • 5.15.203 to ≤ 5.15.*unaffected
  • 6.1.167 to ≤ 6.1.*unaffected
  • 6.6.130 to ≤ 6.6.*unaffected
  • 6.12.43 to ≤ 6.12.*unaffected
  • 6.15.11 to ≤ 6.15.*unaffected
  • 6.16.2 to ≤ 6.16.*unaffected
  • 6.17 to ≤ *unaffected

References