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In the Linux kernel, the following vulnerability has been resolved:
net: ena: fix shift-out-of-bounds in exponential backoff
The ENA adapters on our instances occasionally reset. Once recently logged a UBSAN failure to console in the process:
UBSAN: shift-out-of-bounds in build/linux/drivers/net/ethernet/amazon/ena/ena_com.c:540:13 shift exponent 32 is too large for 32-bit type 'unsigned int' CPU: 28 PID: 70012 Comm: kworker/u72:2 Kdump: loaded not tainted 5.15.117 Hardware name: Amazon EC2 c5d.9xlarge/, BIOS 1.0 10/16/2017 Workqueue: ena ena_fw_reset_device [ena] Call Trace: <TASK> dump_stack_lvl+0x4a/0x63 dump_stack+0x10/0x16 ubsan_epilogue+0x9/0x36 __ubsan_handle_shift_out_of_bounds.cold+0x61/0x10e ? __const_udelay+0x43/0x50 ena_delay_exponential_backoff_us.cold+0x16/0x1e [ena] wait_for_reset_state+0x54/0xa0 [ena] ena_com_dev_reset+0xc8/0x110 [ena] ena_down+0x3fe/0x480 [ena] ena_destroy_device+0xeb/0xf0 [ena] ena_fw_reset_device+0x30/0x50 [ena] process_one_work+0x22b/0x3d0 worker_thread+0x4d/0x3f0 ? process_one_work+0x3d0/0x3d0 kthread+0x12a/0x150 ? set_kthread_struct+0x50/0x50 ret_from_fork+0x22/0x30 </TASK>
Apparently, the reset delays are getting so large they can trigger a UBSAN panic.
Looking at the code, the current timeout is capped at 5000us. Using a base value of 100us, the current code will overflow after (1<<29). Even at values before 32, this function wraps around, perhaps unintentionally.
Cap the value of the exponent used for this backoff at (1<<16) which is larger than currently necessary, but large enough to support bigger values in the future.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Debian | — | Upgrade linux | Sep 17, 2025 | Sep 17, 2025 |
| Huawei Euleros 2_0_sp11 | — | Upgrade kernelUpgrade bpftoolUpgrade kernel-tools-libsUpgrade python3-perfUpgrade kernel-abi-stablelistsUpgrade kernel-tools | Mar 17, 2026 | Mar 17, 2026 |
| Huawei Euleros 2_0_sp13 | — | Upgrade python3-perfUpgrade kernel-abi-stablelistsUpgrade kernel-toolsUpgrade kernelUpgrade kernel-tools-libsUpgrade bpftool | Feb 3, 2026 | Feb 2, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Sep 16, 2025 |
| Ubuntu | — | Upgrade linux-bluefieldUpgrade linux-azure-fdeUpgrade linux-raspiUpgrade linux-aws-5.15Upgrade linux-gcp-5.15Upgrade linux-nvidia-tegraUpgrade linux-lowlatency-hwe-5.15Upgrade linux-gkeUpgrade linux-hwe-5.15Upgrade linux-nvidia-tegra-5.15Upgrade linux-lowlatencyUpgrade linux-oracle-5.15Upgrade linux-intel-iotg-5.15Upgrade linux-realtimeUpgrade linux-azureUpgrade linux-gcpUpgrade linux-xilinx-zynqmpUpgrade linux-oracleUpgrade linux-intel-iot-realtimeUpgrade linux-kvmUpgrade linuxUpgrade linux-riscv-5.15Upgrade linux-gkeopUpgrade linux-azure-5.15Upgrade linux-nvidia-tegra-igxUpgrade linux-nvidiaUpgrade linux-intel-iotgUpgrade linux-awsUpgrade linux-ibm-5.15Upgrade linux-ibm | Sep 19, 2025 | Sep 16, 2025 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Oct 15, 2025 | Sep 16, 2025 |
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