CVE-2026-89747tracing: Fix use-after-free in trace_pipe read on sub-buffer order change

Official description

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix use-after-free in trace_pipe read on sub-buffer order change Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page, and replaces them with newly allocated ones. Readers of trace_pipe hold pointers into those pages. ring_buffer_peek() looks up an event under cpu_buffer->reader_lock but returns the event pointer after dropping the lock, and peek_next_entry() then calls ring_buffer_event_length() and ring_buffer_event_data() on it. If the sub-buffer order is changed in that window, the reader dereferences freed memory: BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430 Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002 Freed by: free_buffer_page kernel/trace/ring_buffer.c:398 [inline] ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444 buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221 Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change. This is the lock trace_pipe readers already hold across their entire peek-and-print loop, so the swap can no longer race with a reader that is dereferencing a peeked event.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/05ebe1e1d7d38c2612bacfefe043a33572ae34cb
• https://git.kernel.org/stable/c/ddbe921ed16a0ad2d9e09574c3f3aabec7528325
• https://git.kernel.org/stable/c/7a49d19ff9baaf61217e5ec14199c18bc2d93ee4
• https://git.kernel.org/stable/c/372f8534244d632ad5118e8a87a11291b01712d3