In the Linux kernel, the following vulnerability has been resolved:
bpf: Add preempt_count_{sub,add} into btf id deny list
The recursion check in __bpf_prog_enter* and __bpf_prog_exit* leave preempt_count_{sub,add} unprotected. When attaching trampoline to them we get panic as follows,
[ 867.843050] BUG: TASK stack guard page was hit at 0000000009d325cf (stack is 0000000046a46a15..00000000537e7b28) [ 867.843064] stack guard page: 0000 [#1] PREEMPT SMP NOPTI [ 867.843067] CPU: 8 PID: 11009 Comm: trace Kdump: loaded Not tainted 6.2.0+ #4 [ 867.843100] Call Trace: [ 867.843101] <TASK> [ 867.843104] asm_exc_int3+0x3a/0x40 [ 867.843108] RIP: 0010:preempt_count_sub+0x1/0xa0 [ 867.843135] __bpf_prog_enter_recur+0x17/0x90 [ 867.843148] bpf_trampoline_6442468108_0+0x2e/0x1000 [ 867.843154] ? preempt_count_sub+0x1/0xa0 [ 867.843157] preempt_count_sub+0x5/0xa0 [ 867.843159] ? migrate_enable+0xac/0xf0 [ 867.843164] __bpf_prog_exit_recur+0x2d/0x40 [ 867.843168] bpf_trampoline_6442468108_0+0x55/0x1000 ... [ 867.843788] preempt_count_sub+0x5/0xa0 [ 867.843793] ? migrate_enable+0xac/0xf0 [ 867.843829] __bpf_prog_exit_recur+0x2d/0x40 [ 867.843837] BUG: IRQ stack guard page was hit at 0000000099bd8228 (stack is 00000000b23e2bc4..000000006d95af35) [ 867.843841] BUG: IRQ stack guard page was hit at 000000005ae07924 (stack is 00000000ffd69623..0000000014eb594c) [ 867.843843] BUG: IRQ stack guard page was hit at 00000000028320f0 (stack is 00000000034b6438..0000000078d1bcec) [ 867.843842] bpf_trampoline_6442468108_0+0x55/0x1000 ...
That is because in __bpf_prog_exit_recur, the preempt_count_{sub,add} are called after prog->active is decreased.
Fixing this by adding these two functions into btf ids deny list.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade bpftool-debuginfoUpgrade kernel-tools-debuginfoUpgrade bpftoolUpgrade python-perfUpgrade kernelUpgrade kernel-toolsUpgrade kernel-debuginfoUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-tools-develUpgrade kernel-livepatch-5.15.117-72.142Upgrade kernel-debuginfo-common-aarch64Upgrade kernel-headersUpgrade python-perf-debuginfoUpgrade kernel-develUpgrade perfUpgrade perf-debuginfo | May 20, 2026 | May 20, 2026 |
| Amazon_linux_2023 | — | Upgrade kernel-debuginfo-common-x86_64Upgrade kernel-toolsUpgrade kernel-headersUpgrade perf-debuginfoUpgrade kernelUpgrade bpftool-debuginfoUpgrade kernel-libbpf-develUpgrade bpftoolUpgrade kernel-debuginfoUpgrade kernel-libbpf-staticUpgrade kernel-libbpfUpgrade perfUpgrade kernel-livepatch-6.1.34-56.100Upgrade kernel-debuginfo-common-aarch64Upgrade python3-perfUpgrade kernel-tools-develUpgrade kernel-tools-debuginfoUpgrade python3-perf-debuginfoUpgrade kernel-devel | Feb 20, 2026 | Dec 24, 2025 |
| Debian | — | Upgrade linux | Dec 29, 2025 | Dec 29, 2025 |
| Huawei Euleros 2_0_sp12 | — | Upgrade kernelUpgrade python3-perfUpgrade kernel-abi-stablelistsUpgrade kernel-tools-libsUpgrade kernel-toolsUpgrade bpftool | Mar 17, 2026 | Mar 16, 2026 |
| Huawei Euleros 2_0_sp13 | — | Upgrade kernel-toolsUpgrade bpftoolUpgrade kernelUpgrade kernel-abi-stablelistsUpgrade python3-perfUpgrade kernel-tools-libs | Mar 10, 2026 | Mar 10, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Dec 24, 2025 |
| Ubuntu | — | Upgrade linux-nvidia-tegra-5.15Upgrade linux-gkeopUpgrade linux-ibm-5.15Upgrade linux-nvidia-tegra-igxUpgrade linux-intel-iot-realtimeUpgrade linux-lowlatencyUpgrade linux-awsUpgrade linuxUpgrade linux-gkeUpgrade linux-azure-fde-5.15Upgrade linux-nvidia-tegraUpgrade linux-kvmUpgrade linux-azure-fdeUpgrade linux-xilinx-zynqmpUpgrade linux-intel-iotgUpgrade linux-ibmUpgrade linux-oracleUpgrade linux-intel-iotg-5.15Upgrade linux-bluefieldUpgrade linux-realtimeUpgrade linux-lowlatency-hwe-5.15Upgrade linux-riscv-5.15Upgrade linux-oracle-5.15Upgrade linux-aws-5.15Upgrade linux-hwe-5.15Upgrade linux-nvidiaUpgrade linux-gcp-5.15Upgrade linux-azureUpgrade linux-raspiUpgrade linux-gcpUpgrade linux-azure-5.15 | Jan 6, 2026 | Dec 24, 2025 |
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