In the Linux kernel, the following vulnerability has been resolved:
x86/Kconfig: make CFI_AUTO_DEFAULT depend on !RUST or Rust >= 1.88
Calling core::fmt::write() from rust code while FineIBT is enabled results in a kernel panic:
[ 4614.199779] kernel BUG at arch/x86/kernel/cet.c:132! [ 4614.205343] Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI [ 4614.211781] CPU: 2 UID: 0 PID: 6057 Comm: dmabuf_dump Tainted: G U O 6.12.17-android16-0-g6ab38c534a43 #1 9da040f27673ec3945e23b998a0f8bd64c846599 [ 4614.227832] Tainted: [U]=USER, [O]=OOT_MODULE [ 4614.241247] RIP: 0010:do_kernel_cp_fault+0xea/0xf0 ... [ 4614.398144] RIP: 0010:_RNvXs5_NtNtNtCs3o2tGsuHyou_4core3fmt3num3impyNtB9_7Display3fmt+0x0/0x20 [ 4614.407792] Code: 48 f7 df 48 0f 48 f9 48 89 f2 89 c6 5d e9 18 fd ff ff 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 41 81 ea 14 61 af 2c 74 03 0f 0b 90 <66> 0f 1f 00 55 48 89 e5 48 89 f2 48 8b 3f be 01 00 00 00 5d e9 e7 [ 4614.428775] RSP: 0018:ffffb95acfa4ba68 EFLAGS: 00010246 [ 4614.434609] RAX: 0000000000000000 RBX: 0000000000000010 RCX: 0000000000000000 [ 4614.442587] RDX: 0000000000000007 RSI: ffffb95acfa4ba70 RDI: ffffb95acfa4bc88 [ 4614.450557] RBP: ffffb95acfa4bae0 R08: ffff0a00ffffff05 R09: 0000000000000070 [ 4614.458527] R10: 0000000000000000 R11: ffffffffab67eaf0 R12: ffffb95acfa4bcc8 [ 4614.466493] R13: ffffffffac5d50f0 R14: 0000000000000000 R15: 0000000000000000 [ 4614.474473] ? __cfi__RNvXs5_NtNtNtCs3o2tGsuHyou_4core3fmt3num3impyNtB9_7Display3fmt+0x10/0x10 [ 4614.484118] ? _RNvNtCs3o2tGsuHyou_4core3fmt5write+0x1d2/0x250
This happens because core::fmt::write() calls core::fmt::rt::Argument::fmt(), which currently has CFI disabled:
library/core/src/fmt/rt.rs: 171 // FIXME: Transmuting formatter in new and indirectly branching to/calling 172 // it here is an explicit CFI violation. 173 #[allow(inline_no_sanitize)] 174 #[no_sanitize(cfi, kcfi)] 175 #[inline] 176 pub(super) unsafe fn fmt(&self, f: &mut Formatter<'_>) -> Result {
This causes a Control Protection exception, because FineIBT has sealed off the original function's endbr64.
This makes rust currently incompatible with FineIBT. Add a Kconfig dependency that prevents FineIBT from getting turned on by default if rust is enabled.
[ Rust 1.88.0 (scheduled for 2025-06-26) should have this fixed [1], and thus we relaxed the condition with Rust >= 1.88.
When `objtool` lands checking for this with e.g. [2], the plan is to ideally run that in upstream Rust's CI to prevent regressions early [3], since we do not control `core`'s source code.
Alice tested the Rust PR backported to an older compiler.
Peter would like that Rust provides a stable `core` which can be pulled into the kernel: "Relying on that much out of tree code is 'unfortunate'".
- Miguel ]
[ Reduced splat. - Miguel ]
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade kernel-livepatch-6.12.31-35.92Upgrade kernel-toolsUpgrade bpftoolUpgrade kernel-libbpf-staticUpgrade kernel-tools-debuginfoUpgrade kernel-libbpf-debuginfoUpgrade kernel6.12-debuginfo-common-x86_64Upgrade python3-perf6.12Upgrade kernel-libbpfUpgrade kernel-tools-develUpgrade perf6.12-debuginfoUpgrade kernel-develUpgrade kernel-modules-extra-commonUpgrade kernel-libbpf-develUpgrade python3-perf6.12-debuginfoUpgrade kernel-headersUpgrade perf6.12Upgrade kernel6.12Upgrade kernel6.12-modules-extraUpgrade bpftool-debuginfoUpgrade kernel6.12-debuginfo-common-aarch64Upgrade kernel6.12-debuginfo | Aug 5, 2025 | Jun 18, 2025 |
| Debian | — | Upgrade linuxNo solution exists | Jun 20, 2025 | Jun 18, 2025 |
| Ubuntu | — | Upgrade linux-image-oracleUpgrade linux-image-6.14.0-1016-gcpUpgrade linux-image-6.14.0-1014-raspiUpgrade linux-image-oem-24.04bUpgrade linux-image-generic-64k-hwe-24.04Upgrade linux-image-oem-24.04Upgrade linux-image-6.14.0-1012-azureUpgrade linux-image-oem-6.14Upgrade linux-image-genericUpgrade linux-image-6.14.0-1016-gcp-64kUpgrade linux-image-generic-64kUpgrade linux-image-oracle-6.14Upgrade linux-image-virtualUpgrade linux-image-azure-6.14Upgrade linux-image-6.14.0-32-genericUpgrade linux-image-oracle-64k-6.14Upgrade linux-image-generic-6.14Upgrade linux-image-6.14.0-1013-awsUpgrade linux-image-6.14.0-1013-oracleUpgrade linux-image-gcp-64k-6.14Upgrade linux-image-aws-64kUpgrade linux-image-6.14.0-1012-realtimeUpgrade linux-image-raspi-6.14Upgrade linux-image-realtime-hwe-24.04Upgrade linux-image-oem-24.04aUpgrade linux-image-generic-hwe-24.04Upgrade linux-image-aws-6.14Upgrade linux-image-6.14.0-32-generic-64kUpgrade linux-image-6.14.0-1013-oracle-64kUpgrade linux-image-virtual-hwe-24.04Upgrade linux-image-virtual-6.14Upgrade linux-image-realtimeUpgrade linux-image-gcp-6.14Upgrade linux-image-awsUpgrade linux-image-oem-24.04cUpgrade linux-image-6.14.0-1012-oemUpgrade linux-image-gcp-64kUpgrade linux-image-gcpUpgrade linux-image-aws-64k-6.14Upgrade linux-image-oracle-64kUpgrade linux-image-generic-64k-6.14Upgrade linux-image-raspiUpgrade linux-image-realtime-6.14Upgrade linux-image-azureUpgrade linux-image-6.14.0-1013-aws-64k | Jun 26, 2025 | Jun 18, 2025 |
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