In the Linux kernel, the following vulnerability has been resolved:
cifs: fix potential oops in cifs_oplock_break
With deferred close we can have closes that race with lease breaks, and so with the current checks for whether to send the lease response, oplock_response(), this can mean that an unmount (kill_sb) can occur just before we were checking if the tcon->ses is valid. See below:
[Fri Aug 4 04:12:50 2023] RIP: 0010:cifs_oplock_break+0x1f7/0x5b0 [cifs] [Fri Aug 4 04:12:50 2023] Code: 7d a8 48 8b 7d c0 c0 e9 02 48 89 45 b8 41 89 cf e8 3e f5 ff ff 4c 89 f7 41 83 e7 01 e8 82 b3 03 f2 49 8b 45 50 48 85 c0 74 5e <48> 83 78 60 00 74 57 45 84 ff 75 52 48 8b 43 98 48 83 eb 68 48 39 [Fri Aug 4 04:12:50 2023] RSP: 0018:ffffb30607ddbdf8 EFLAGS: 00010206 [Fri Aug 4 04:12:50 2023] RAX: 632d223d32612022 RBX: ffff97136944b1e0 RCX: 0000000080100009 [Fri Aug 4 04:12:50 2023] RDX: 0000000000000001 RSI: 0000000080100009 RDI: ffff97136944b188 [Fri Aug 4 04:12:50 2023] RBP: ffffb30607ddbe58 R08: 0000000000000001 R09: ffffffffc08e0900 [Fri Aug 4 04:12:50 2023] R10: 0000000000000001 R11: 000000000000000f R12: ffff97136944b138 [Fri Aug 4 04:12:50 2023] R13: ffff97149147c000 R14: ffff97136944b188 R15: 0000000000000000 [Fri Aug 4 04:12:50 2023] FS: 0000000000000000(0000) GS:ffff9714f7c00000(0000) knlGS:0000000000000000 [Fri Aug 4 04:12:50 2023] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [Fri Aug 4 04:12:50 2023] CR2: 00007fd8de9c7590 CR3: 000000011228e000 CR4: 0000000000350ef0 [Fri Aug 4 04:12:50 2023] Call Trace: [Fri Aug 4 04:12:50 2023] <TASK> [Fri Aug 4 04:12:50 2023] process_one_work+0x225/0x3d0 [Fri Aug 4 04:12:50 2023] worker_thread+0x4d/0x3e0 [Fri Aug 4 04:12:50 2023] ? process_one_work+0x3d0/0x3d0 [Fri Aug 4 04:12:50 2023] kthread+0x12a/0x150 [Fri Aug 4 04:12:50 2023] ? set_kthread_struct+0x50/0x50 [Fri Aug 4 04:12:50 2023] ret_from_fork+0x22/0x30 [Fri Aug 4 04:12:50 2023] </TASK>
To fix this change the ordering of the checks before sending the oplock_response to first check if the openFileList is empty.
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade perf-debuginfoUpgrade python-perfUpgrade kernel-headersUpgrade kernel-toolsUpgrade perfUpgrade kernel-debuginfoUpgrade kernel-develUpgrade bpftool-debuginfoUpgrade kernel-debuginfo-common-aarch64Upgrade python-perf-debuginfoUpgrade kernel-tools-debuginfoUpgrade kernel-tools-develUpgrade kernel-livepatch-5.15.128-80.144Upgrade kernel-debuginfo-common-x86_64Upgrade bpftoolUpgrade kernel | May 20, 2026 | May 20, 2026 |
| Amazon_linux_2023 | — | Upgrade kernelUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-livepatch-6.1.49-69.116Upgrade kernel-libbpf-develUpgrade kernel-libbpf-staticUpgrade python3-perf-debuginfoUpgrade bpftool-debuginfoUpgrade kernel-headersUpgrade python3-perfUpgrade perfUpgrade kernel-libbpfUpgrade kernel-tools-debuginfoUpgrade kernel-tools-develUpgrade kernel-debuginfoUpgrade bpftoolUpgrade kernel-debuginfo-common-aarch64Upgrade perf-debuginfoUpgrade kernel-toolsUpgrade kernel-devel | Feb 20, 2026 | Dec 30, 2025 |
| Debian | — | Upgrade linux | Jul 27, 2026 | Jul 27, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Dec 30, 2025 |
| Ubuntu | — | Upgrade linuxUpgrade linux-ibmUpgrade linux-lowlatencyUpgrade linux-ibm-5.15Upgrade linux-xilinx-zynqmpUpgrade linux-oracle-5.15Upgrade linux-oracleUpgrade linux-azure-5.15Upgrade linux-nvidiaUpgrade linux-nvidia-tegra-igxUpgrade linux-gkeUpgrade linux-gkeopUpgrade linux-azure-fdeUpgrade linux-awsUpgrade linux-gcpUpgrade linux-intel-iotgUpgrade linux-raspiUpgrade linux-azureUpgrade linux-realtimeUpgrade linux-hwe-5.15Upgrade linux-nvidia-tegraUpgrade linux-gcp-5.15Upgrade linux-bluefieldUpgrade linux-intel-iotg-5.15Upgrade linux-kvmUpgrade linux-aws-5.15Upgrade linux-nvidia-tegra-5.15Upgrade linux-intel-iot-realtimeUpgrade linux-lowlatency-hwe-5.15Upgrade linux-riscv-5.15 | Jan 6, 2026 | Jan 2, 2026 |
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