Executive brief
A diagnostic issue was identified in the Linux kernel's block layer where the system would trigger unnecessary 'kernel warning' alerts during normal but stressful operations, such as low memory conditions. While these warnings do not represent a security breach or a system crash, they can clutter system logs and interfere with automated monitoring tools. The fix ensures the system handles these expected scenarios gracefully without triggering false-positive emergency alerts.
Technical details
The vulnerability (or rather, diagnostic bug) exists in the `wbt_init_enable_default()` function within `block/blk-wbt.c`. The code used `WARN_ON_ONCE` to handle expected failure returns from `wbt_alloc()` (which can return NULL under memory pressure) and `wbt_init()` (which can return -EBUSY if already registered). An attacker or automated fuzzer (like syzbot) could trigger these warnings by injecting memory allocation failures during MTD partition creation via `ioctl(BLKPG)`. The fix replaces the `WARN_ON_ONCE` macros with standard conditional checks and a `pr_warn()` call, preventing unnecessary stack traces while maintaining diagnostic visibility.
Affected products
- Linux Linux Kernel 7.0, 7.0.10, 7.1
Timeline
- 2026-03-16: other: Patch authored
- 2026-06-26: disclosed: CVE published