In the Linux kernel, the following vulnerability has been resolved:
sched/core: Fix use-after-free bug in dup_user_cpus_ptr()
Since commit 07ec77a1d4e8 ("sched: Allow task CPU affinity to be restricted on asymmetric systems"), the setting and clearing of user_cpus_ptr are done under pi_lock for arm64 architecture. However, dup_user_cpus_ptr() accesses user_cpus_ptr without any lock protection. Since sched_setaffinity() can be invoked from another process, the process being modified may be undergoing fork() at the same time. When racing with the clearing of user_cpus_ptr in __set_cpus_allowed_ptr_locked(), it can lead to user-after-free and possibly double-free in arm64 kernel.
Commit 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask") fixes this problem as user_cpus_ptr, once set, will never be cleared in a task's lifetime. However, this bug was re-introduced in commit 851a723e45d1 ("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()") which allows the clearing of user_cpus_ptr in do_set_cpus_allowed(). This time, it will affect all arches.
Fix this bug by always clearing the user_cpus_ptr of the newly cloned/forked task before the copying process starts and check the user_cpus_ptr state of the source task under pi_lock.
Note to stable, this patch won't be applicable to stable releases. Just copy the new dup_user_cpus_ptr() function over.
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade kernel-toolsUpgrade bpftool-debuginfoUpgrade python-perf-debuginfoUpgrade python-perfUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-tools-develUpgrade kernel-tools-debuginfoUpgrade bpftoolUpgrade kernel-debuginfoUpgrade kernelUpgrade perf-debuginfoUpgrade perfUpgrade kernel-debuginfo-common-aarch64Upgrade kernel-livepatch-5.15.90-54.138Upgrade kernel-headersUpgrade kernel-devel | Sep 27, 2024 | Aug 21, 2024 |
| Debian | — | Upgrade linux | Aug 22, 2024 | Aug 22, 2024 |
| Redhat_linux | — | No solution exists | Jul 9, 2025 | Aug 21, 2024 |
| Ubuntu | — | Upgrade linuxUpgrade linux-raspiUpgrade linux-lowlatencyUpgrade linux-azure-fdeUpgrade linux-realtimeUpgrade linux-lowlatency-hwe-5.15Upgrade linux-awsUpgrade linux-aws-5.15Upgrade linux-riscv-5.15Upgrade linux-gkeUpgrade linux-bluefieldUpgrade linux-hwe-5.15Upgrade linux-gcpUpgrade linux-azure-fde-5.15Upgrade linux-intel-iotgUpgrade linux-oracleUpgrade linux-azureUpgrade linux-gcp-5.15Upgrade linux-intel-iotg-5.15Upgrade linux-azure-5.15Upgrade linux-kvmUpgrade linux-ibmUpgrade linux-oracle-5.15Upgrade linux-intel-iot-realtimeUpgrade linux-gkeop-5.15Upgrade linux-gkeopUpgrade linux-nvidia | Nov 19, 2024 | Aug 21, 2024 |
Prioritise with Active Threat Intelligence
With curated Threat Intelligence, you can see which vulnerabilities truly put you at risk, prioritize what matters most, and act before attackers do.
Explore Intelligence Hub