UBUNTU-CVE-2026-98800: High severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: bpf: Wait for an RCU tasks grace period before freeing trampoline progs When a prog is detached from a trampoline, it is freed after an RCU grace period, or an RCU tasks trace one if it is sleepable. This covers the tasks that are running the prog, since the prog's enter helper takes the matching read lock before the prog is called. On a preemptible kernel, it doesn't cover a task that was preempted in the trampoline just before the enter helper. That task holds no lock yet, and it calls the prog after it was freed: BUG: KASAN: vmalloc-out-of-bounds in bpfprogenterrecur+0x3a5/0x3f0 Read of size 8 at addr ffffc90000055040 by task candidate/110 CPU: 1 UID: 0 PID: 110 Comm: candidate Not tainted 7.3.0-rc2-00014-g15071f2a1263-dirty #2 PREEMPT(full) Call Trace: <TASK> bpfprogenterrecur+0x3a5/0x3f0 bpftrampoline6442509193+0x37/0xf1 x64sysfutex+0x9/0x410 dosyscall64+0xb0/0x530 ... Wait for an RCU tasks grace period before the existing one when freeing a prog that was linked to a trampoline. An RCU tasks grace period only ends once the tasks that were preempted have run again, and bpftrampimageput() already relies on it to free the image. It doesn't wait for tasks that sleep in the trampoline, the next commit takes care of those. Only progs that were linked to a trampoline can be called this way, so bpftrampolineaddprog() marks them and other progs are still freed as before.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.18~24.04.1 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1019.19~24.04.1 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.19~24.04.1 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.18~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-43.43.1~24.04.2 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-43.43 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1017.18 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1020.21 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1019.19 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1017.19 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1010.11 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1018.18 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1018.18 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-43.43.1 - Compensating control
Wait for an RCU tasks grace period before the existing grace period when freeing a BPF program that was linked to a trampoline.
Event History
Frequently Asked Questions
What conditions are required to trigger this issue?
An attacker or local user would need high privileges and the ability to detach a BPF program from a trampoline while another task has been preempted in the trampoline immediately before entering the program. The affected scenario is specifically on preemptible kernels.
What is the likely impact if the race is triggered?
A preempted task can later call a BPF program after it has been freed, causing an out-of-bounds read. The reported impact includes high confidentiality, integrity, and availability effects.
Which Ubuntu kernel packages should be reviewed?
Review systems using ubuntu/linux, ubuntu/linux-realtime, ubuntu/linux-azure, ubuntu/linux-gcp, ubuntu/linux-azure-fde, ubuntu/linux-gke, ubuntu/linux-riscv, or ubuntu/linux-gkeop.
How can I identify whether this condition has occurred?
The provided report shows a KASAN vmalloc out-of-bounds read in __bpf_prog_enter_recur, with a BPF trampoline function in the call trace. Look for similar kernel reports involving a task resuming through a trampoline after a BPF program was detached.