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CVE-2026-89503: ring-buffer: Fix subbuf resize race with ring_buffer_alloc_read_page()

• Severity: high (CVSS 7.8 v3.1)
• 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: 2026-09-11 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Fix subbuf resize race with ring_buffer_alloc_read_page() ring_buffer_alloc_read_page() is racy with ring_buffer_subbuf_order_set, it can allocate a reader page with an outdated order. This isn't a big issue, the user can still re-allocate a new reader page and try again. However, what is more problematic is if the value of subbuf_order changes in the middle of ring_buffer_alloc_read_page(). In that case, bpage->order might not match the actual allocated memory. Use bpage->order for the allocation to prevent this race.

Affected products

• Linux kernel: 6.8 — fixed in 7.3

How to fix

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

References

• https://git.kernel.org/stable/c/2313ff69bd237aad264a5913907f374f958335a2
• https://git.kernel.org/stable/c/2dc510957fe8fd098ab3c3147ebdf34d00cd2734
• https://git.kernel.org/stable/c/53106e9262a310ef2c9a9321168c03705940c678
• https://git.kernel.org/stable/c/e743527c5bfdceda1095bc0a9e596e2aebb6a9c3

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