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

blk-wbt: remove WARN_ON_ONCE from wbt_init_enable_default()

wbt_init_enable_default() uses WARN_ON_ONCE to check for failures from
wbt_alloc() and wbt_init(). However, both are expected failure paths:

• wbt_alloc() can return NULL under memory pressure (-ENOMEM)
• wbt_init() can fail with -EBUSY if wbt is already registered

syzbot triggers this by injecting memory allocation failures during MTD
partition creation via ioctl(BLKPG), causing a spurious warning.

wbt_init_enable_default() is a best-effort initialization called from
blk_register_queue() with a void return type. Failure simply means the
disk operates without writeback throttling, which is harmless.

Replace WARN_ON_ONCE with plain if-checks, consistent with how
wbt_set_lat() in the same file already handles these failures. Add a
pr_warn() for the wbt_init() failure to retain diagnostic information
without triggering a full stack trace.

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-53319
• https://git.kernel.org/stable/c/e9b004ff83067cdf96774b45aea4b239ace99a2f
• https://git.kernel.org/stable/c/fd7a982657077469802594a5165bc30b9a55af70