CVE-2026-89748tracing: Fix retry exhaustion in simple ring buffer reader swap

Official description

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. The current !retry test reverses both outcomes. It returns an error after a successful final replacement, leaving the link update complete but the reader bookkeeping unfinished. After a failed final replacement, it falls through and updates the head and reader pointers as though the replacement succeeded, which can corrupt the ring. Treat only a negative counter as exhaustion and return the documented -EBUSY error.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/df02489aa3aa1834659f0d20c89f7d212047d268
• https://git.kernel.org/stable/c/e0d3aed7b12cf37b74c7cc5265073d0263b49cde