CVE-2024-46704
Medium · 4.7CVSS
4.7
EPSS
0.2%
Published
Sep 13, 2024
CISA due date
—
Cloudanix analysis
A small reordering of checks inside the Linux kernel's task handling code stops a checker tool from raising false alarms, but the system itself keeps working exactly as before.
- Exploitation
- Other
- Attacker needs
- None
- Complexity
- Theoretical
- Impact
- Other
- Component
- OS kernel
- Class
- Race Condition
- Remediation
- Patch
- Effort
- Low
- Patch risk
- None
What it actually does
Code in __flush_work() read work->data before testing the from_cancel flag, allowing KCSAN to report a spurious concurrent access on the work item during flushing or cancellation even though the read value was unused when not canceling.
Why it matters to the business
Kernel developers and CI systems using KCSAN encounter repeated false-positive race reports, wasting triage time on a non-issue with zero runtime, stability, or security consequences; prevalence in the Linux kernel and Cilium increases exposure for organizations building or running container networking stacks.
How an attack unfolds
No attacker can exploit this because the reported race is an artifact of code ordering rather than a real data race; the change merely reorders the from_cancel test ahead of the data read to silence KCSAN without altering behavior.
How to fix it
Upgrade the Linux kernel to commit 91d09642127a32fde231face2ff489af70eef316 or later; for Cilium deployments update to 1.14.12, 1.13.17, or 1.15.6.
How to confirm the fix worked
Confirm the source change that tests from_cancel before dereferencing work->data in __flush_work(); re-run KCSAN on the workqueue paths and verify absence of the previous false-positive report.
How to detect it
Not applicable; the original condition produced only static-analysis noise and left no runtime artifacts or logs indicating exploitation.
What your security team should do
- Apply the listed kernel and Cilium updates at the next maintenance window
- Review KCSAN results after upgrade to close any related tickets
- Monitor EPSS and KEV status for any future changes in exploitability signals
The record
In the Linux kernel, the following vulnerability has been resolved: workqueue: Fix spruious data race in __flush_work() When flushing a work item for cancellation, __flush_work() knows that it exclusively owns the work item through its PENDING bit. 134874e2eee9 ("workqueue: Allow cancel_work_sync() and disable_work() from atomic contexts on BH work items") added a read of @work->data to determine whether to use busy wait for BH work items that are being canceled. While the read is safe when @from_cancel, @work->data was read before testing @from_cancel to simplify code structure: data = *work_data_bits(work); if (from_cancel && !WARN_ON_ONCE(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_BH)) { While the read data was never used if !@from_cancel, this could trigger KCSAN data race detection spuriously: ================================================================== BUG: KCSAN: data-race in __flush_work / __flush_work write to 0xffff8881223aa3e8 of 8 bytes by task 3998 on cpu 0: instrument_write include/linux/instrumented.h:41 [inline] ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [inline] insert_wq_barrier kernel/workqueue.c:3790 [inline] start_flush_work kernel/workqueue.c:4142 [inline] __flush_work+0x30b/0x570 kernel/workqueue.c:4178 flush_work kernel/workqueue.c:4229 [inline] ... read to 0xffff8881223aa3e8 of 8 bytes by task 50 on cpu 1: __flush_work+0x42a/0x570 kernel/workqueue.c:4188 flush_work kernel/workqueue.c:4229 [inline] flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251 ... value changed: 0x0000000000400000 -> 0xffff88810006c00d Reorganize the code so that @from_cancel is tested before @work->data is accessed. The only problem is triggering KCSAN detection spuriously. This shouldn't need READ_ONCE() or other access qualifiers. No functional changes.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Debian:13 | linux | 0 | 6.10.7-1 |
| Linux | Kernel | 6.10.0 | 6.10.7 |
| Ubuntu:16.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-aws-5.0 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-aws-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gcp | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gcp-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gke-4.15 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gke-5.4 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gkeop-5.4 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-hwe | 0 | No fix |
| Ubuntu:18.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oem | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oracle-5.0 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oracle-5.3 | 0 | No fix |
| Ubuntu:20.04:LTS | linux | 0 | 5.4.0-9.12 |
| Ubuntu:20.04:LTS | linux-aws | 0 | 5.4.0-1005.5 |
| Ubuntu:20.04:LTS | linux-aws-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-aws-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-aws-5.15 | 0 | 5.15.0-1014.18~20.04.1 |
| Ubuntu:20.04:LTS | linux-aws-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure | 0 | 5.4.0-1006.6 |
| Ubuntu:20.04:LTS | linux-azure-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.15 | 0 | 5.15.0-1007.8~20.04.1 |
| Ubuntu:20.04:LTS | linux-azure-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-fde | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-fde-5.15 | 0 | 5.15.0-1019.24~20.04.1.1 |
| Ubuntu:20.04:LTS | linux-bluefield | 0 | 5.4.0-1007.10 |
| Ubuntu:20.04:LTS | linux-gcp | 0 | 5.4.0-1005.5 |
| Ubuntu:20.04:LTS | linux-gcp-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gcp-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gcp-5.15 | 0 | 5.15.0-1006.9~20.04.1 |
| Ubuntu:20.04:LTS | linux-gcp-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gke | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gke-5.15 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gkeop | 0 | 5.4.0-1008.9 |
| Ubuntu:20.04:LTS | linux-gkeop-5.15 | 0 | 5.15.0-1003.5~20.04.2 |
| Ubuntu:20.04:LTS | linux-hwe-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.15 | 0 | 5.15.0-33.34~20.04.1 |
| Ubuntu:20.04:LTS | linux-hwe-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-ibm | 0 | 5.4.0-1003.4 |
| Ubuntu:20.04:LTS | linux-ibm-5.15 | 0 | 5.15.0-1033.36~20.04.1 |
| Ubuntu:20.04:LTS | linux-intel-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-intel-iotg-5.15 | 0 | 5.15.0-1003.5~20.04.1 |
| Ubuntu:20.04:LTS | linux-iot | 0 | 5.4.0-1001.3 |
| Ubuntu:20.04:LTS | linux-kvm | 0 | 5.4.0-1004.4 |
| Ubuntu:20.04:LTS | linux-lowlatency-hwe-5.15 | 0 | 5.15.0-33.34~20.04.1 |
| Ubuntu:20.04:LTS | linux-oem-5.10 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.14 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.6 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle | 0 | 5.4.0-1005.5 |
| Ubuntu:20.04:LTS | linux-oracle-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle-5.15 | 0 | 5.15.0-1007.9~20.04.1 |
| Ubuntu:20.04:LTS | linux-oracle-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-raspi | 0 | 5.4.0-1007.7 |
| Ubuntu:20.04:LTS | linux-raspi2 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv-5.15 | 0 | 5.15.0-1015.17~20.04.1 |
| Ubuntu:20.04:LTS | linux-riscv-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-xilinx-zynqmp | 0 | 5.4.0-1020.24 |
| Ubuntu:22.04:LTS | linux | 0 | 5.13.0-19.19 |
| Ubuntu:22.04:LTS | linux-allwinner-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws | 0 | 5.13.0-1005.6 |
| Ubuntu:22.04:LTS | linux-aws-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure | 0 | 5.13.0-1006.7 |
| Ubuntu:22.04:LTS | linux-azure-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-fde | 0 | 5.15.0-1019.24.1 |
| Ubuntu:22.04:LTS | linux-azure-fde-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-fde-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp | 0 | 5.13.0-1005.6 |
| Ubuntu:22.04:LTS | linux-gcp-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gke | 0 | 5.15.0-1002.2 |
| Ubuntu:22.04:LTS | linux-gkeop | 0 | 5.15.0-1001.2 |
| Ubuntu:22.04:LTS | linux-hwe-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.8 | 0 | 6.8.0-38.38~22.04.1 |
| Ubuntu:22.04:LTS | linux-ibm | 0 | 5.15.0-1002.2 |
| Ubuntu:22.04:LTS | linux-intel-iot-realtime | 0 | No fix |
| Ubuntu:22.04:LTS | linux-intel-iot-realtime | 0 | 5.15.0-1021.26 |
| Ubuntu:22.04:LTS | linux-intel-iotg | 0 | 5.15.0-1004.6 |
| Ubuntu:22.04:LTS | linux-kvm | 0 | 5.13.0-1004.4 |
| Ubuntu:22.04:LTS | linux-lowlatency | 0 | 5.15.0-22.22 |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.8 | 0 | 6.8.0-38.38.1~22.04.2 |
| Ubuntu:22.04:LTS | linux-nvidia | 0 | 5.15.0-1005.5 |
| Ubuntu:22.04:LTS | linux-nvidia-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-nvidia-6.5 | 0 | 6.5.0-1004.4 |
| Ubuntu:22.04:LTS | linux-nvidia-6.8 | 0 | 6.8.0-1008.8~22.04.1 |
| Ubuntu:22.04:LTS | linux-oem-5.17 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.0 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.1 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oracle | 0 | 5.13.0-1008.10 |
| Ubuntu:22.04:LTS | linux-oracle-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-raspi | 0 | 5.13.0-1008.9 |
| Ubuntu:22.04:LTS | linux-realtime | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-6.8 | 0 | 6.8.0-38.38.1~22.04.1 |
| Ubuntu:22.04:LTS | linux-starfive-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-starfive-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-starfive-6.5 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-xilinx-zynqmp | 0 | 5.15.0-1022.26 |
| Ubuntu:22.04:LTS:for:NVIDIA:BlueField | linux-bluefield | 0 | 5.15.0-1011.13 |
| Ubuntu:24.04:LTS | linux | 0 | 6.5.0-9.9 |
| Ubuntu:24.04:LTS | linux-aws | 0 | 6.5.0-1008.8 |
| Ubuntu:24.04:LTS | linux-azure | 0 | 6.5.0-1007.7 |
| Ubuntu:24.04:LTS | linux-gcp | 0 | 6.5.0-1007.7 |
| Ubuntu:24.04:LTS | linux-gke | 0 | 6.8.0-1003.5 |
| Ubuntu:24.04:LTS | linux-gkeop | 0 | 6.8.0-1001.3 |
| Ubuntu:24.04:LTS | linux-ibm | 0 | 6.5.0-1009.9 |
| Ubuntu:24.04:LTS | linux-lowlatency | 0 | 6.5.0-9.9.1 |
| Ubuntu:24.04:LTS | linux-nvidia | 0 | 6.8.0-1007.7 |
| Ubuntu:24.04:LTS | linux-nvidia-lowlatency | 0 | 6.8.0-1009.9.1 |
| Ubuntu:24.04:LTS | linux-oem-6.8 | 0 | 6.8.0-1003.3 |
| Ubuntu:24.04:LTS | linux-oracle | 0 | 6.5.0-1010.10 |
| Ubuntu:24.04:LTS | linux-raspi | 0 | 6.5.0-1005.7 |
| Ubuntu:24.04:LTS | linux-raspi-realtime | 0 | No fix |
| Ubuntu:24.04:LTS | linux-raspi-realtime | 0 | 6.7.0-2001.1 |
| Ubuntu:24.04:LTS | linux-realtime | 0 | 6.8.0-1008.19 |
| Ubuntu:24.04:LTS | linux-riscv | 0 | 6.5.0-9.9.1 |
| Ubuntu:Pro:16.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-aws-5.0 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-aws-5.3 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-azure | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-azure-5.3 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-azure-edge | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gcp | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gcp-5.3 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gke-4.15 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gke-5.4 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gkeop-5.4 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-hwe | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-oem | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-oracle-5.0 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-oracle-5.3 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-aws-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-aws-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-aws-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-fde | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gcp-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gcp-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gcp-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gke | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gke-5.15 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-hwe-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-hwe-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-hwe-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-intel-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.10 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.14 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.6 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oracle-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oracle-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oracle-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-raspi2 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-riscv-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-riscv-5.8 | 0 | No fix |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-aws-fips | 0 | 5.15.0-1051.56+fips1 |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-azure-fips | 0 | 5.15.0-1053.61+fips1 |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-fips | 0 | 5.15.0-73.80+fips1 |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-gcp-fips | 0 | 5.15.0-1048.56+fips1 |
| Ubuntu:Pro:FIPS-updates:18.04:LTS | linux-aws-fips | 0 | 4.15.0-2000.4 |
| Ubuntu:Pro:FIPS-updates:18.04:LTS | linux-azure-fips | 0 | 4.15.0-1002.2 |
| Ubuntu:Pro:FIPS-updates:18.04:LTS | linux-fips | 0 | 4.15.0-1027.32 |
| Ubuntu:Pro:FIPS-updates:18.04:LTS | linux-gcp-fips | 0 | 4.15.0-2013.14 |
| Ubuntu:Pro:FIPS-updates:20.04:LTS | linux-aws-fips | 0 | 5.4.0-1021.21+fips2 |
| Ubuntu:Pro:FIPS-updates:20.04:LTS | linux-azure-fips | 0 | 5.4.0-1022.22+fips1 |
| Ubuntu:Pro:FIPS-updates:20.04:LTS | linux-fips | 0 | 5.4.0-1026.30 |
| Ubuntu:Pro:FIPS-updates:20.04:LTS | linux-gcp-fips | 0 | 5.4.0-1021.21+fips1 |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-aws-fips | 0 | 5.15.0-1052.57+fips1 |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-azure-fips | 0 | 5.15.0-1058.66+fips1 |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-fips | 0 | 5.15.0-92.102+fips1 |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-gcp-fips | 0 | 5.15.0-1048.56+fips1 |
| Ubuntu:Pro:FIPS:16.04:LTS | linux-fips | 0 | 4.4.0-1003.3 |
| Ubuntu:Pro:FIPS:18.04:LTS | linux-aws-fips | 0 | 4.15.0-2000.4 |
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