tracing: Fix retry exhaustion in simple ring buffer reader swap

Overview

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

• Linux >= 34e5b958bdad0f9cf16306368bbc2dc5b2a50143 < df02489aa3aa1834659f0d20c89f7d212047d268
• Linux >= 34e5b958bdad0f9cf16306368bbc2dc5b2a50143 < e0d3aed7b12cf37b74c7cc5265073d0263b49cde
• Linux 7.1

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Moderate · updated 2026-09-21 · vex