CVE-2026-74365: nvdimm/btt: Handle preemption in BTT lane acquisition

Severity: high (CVSS 7.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-15 · updated 2026-10-16

Description

In the Linux kernel, the following vulnerability has been resolved: nvdimm/btt: Handle preemption in BTT lane acquisition BTT lanes serialize access to per-lane metadata and workspace state during BTT I/O. The btt-check unit test reports data mismatches during BTT writes due to a race in lane acquisition that can lead to silent data corruption. The existing lane model uses a spinlock together with a per-CPU recursion count. That recursion model stopped being valid after BTT lanes became preemptible: another task can run on the same CPU, observe a non-zero recursion count, bypass locking, and use the same lane concurrently. BTT lanes are also held across arena_write_bytes() calls. That path reaches nsio_rw_bytes(), which flushes writes with nvdimm_flush(). Some provider flush callbacks can sleep, making a spinlock the wrong primitive for the lane lifetime. Replace the spinlock-based recursion model with a dynamically allocated per-lane mutex array and take the lane lock unconditionally. Add might_sleep() to catch any future atomic-context caller. Found with the ndctl unit test btt-check.sh.

Affected products

Linux kernel: from 6.1.63 before 6.1.178; from 6.6.2 before 6.6.145; from 4.19.299 before 4.20; from 5.4.261 before 5.5; from 5.10.201 before 5.11; from 5.15.139 before 5.16 — fixed in 4.20, 5.11, 5.16, 5.5, 6.1.178, 6.6

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.11, 5.16, 5.5. Check the vendor advisory for mitigations.

References

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