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CVE-2026-90066: samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify ftrace_direct_multi_init() assigns kthread_run()'s return value to simple_tsk without an IS_ERR() check. When kthread_run() fails it returns ERR_PTR(-ENOMEM), but init still returns 0, so the module loads with simple_tsk holding an error pointer. On unload, ftrace_direct_multi_exit() then passes that ERR_PTR to kthread_stop(), leading to a null-pointer-dereference. Check the return value of kthread_run() with IS_ERR(); on failure, unregister the ftrace direct call and propagate the error code.

Affected products

• Linux: 5.16 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/02866f063062dcc5686445c738be003de9787250
• https://git.kernel.org/stable/c/626614df9080d7052fbe24dc90b5434717ab7a9f
• https://git.kernel.org/stable/c/6727b7618f49401acf373fa3ec5712e2ec52e5cf
• https://git.kernel.org/stable/c/7a96b9f6d5ba23dbce66c8a4a242effd4c01a830
• https://git.kernel.org/stable/c/98b7b2a29ae87937aa02ab9391543ef8c602cd94
• https://git.kernel.org/stable/c/cf839636911d8313f3ecd098329fd0b96499e4cf

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