ring-buffer: Check resize_disabled before publishing the new subbuf order

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Check resize_disabled before publishing the new subbuf order ring_buffer_subbuf_order_set() stores the new order and only then walks the CPUs, returning -EBUSY if any of them has resizing disabled. A user mapped buffer has resizing disabled, and __rb_map_vma() reads buffer->subbuf_order without buffer->mutex, so an mmap of an already mapped CPU racing the failing order change sizes the mapping with the new order and inserts pages past the sub-buffer into the VMA. Check the CPUs before storing the new order.

Source published

25 Sep 2026 10:22:24 UTC

Source modified

19 Oct 2026 09:10:20 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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