CVE-2025-38267 — ring-buffer: Do not trigger WARN_ON() due to a commit_overrun

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

ring-buffer: Do not trigger WARN_ON() due to a commit_overrun

When reading a memory mapped buffer the reader page is just swapped out with the last page written in the write buffer. If the reader page is the same as the commit buffer (the buffer that is currently being written to) it was assumed that it should never have missed events. If it does, it triggers a WARN_ON_ONCE().

But there just happens to be one scenario where this can legitimately happen. That is on a commit_overrun. A commit overrun is when an interrupt preempts an event being written to the buffer and then the interrupt adds so many new events that it fills and wraps the buffer back to the commit. Any new events would then be dropped and be reported as "missed_events".

In this case, the next page to read is the commit buffer and after the swap of the reader page, the reader page will be the commit buffer, but this time there will be missed events and this triggers the following warning:

------------[ cut here ]------------ WARNING: CPU: 2 PID: 1127 at kernel/trace/ring_buffer.c:7357 ring_buffer_map_get_reader+0x49a/0x780 Modules linked in: kvm_intel kvm irqbypass CPU: 2 UID: 0 PID: 1127 Comm: trace-cmd Not tainted 6.15.0-rc7-test-00004-g478bc2824b45-dirty #564 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:ring_buffer_map_get_reader+0x49a/0x780 Code: 00 00 00 48 89 fe…

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CVE-2025-38267 — ring-buffer: Do not trigger WARN_ON() due to a commit_overrun