CVE-2026-53393

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> nfsd: reset write verifier on deferred writeback errors<br /> <br /> nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to<br /> detect deferred writeback errors, but neither rotates the server&amp;#39;s write<br /> verifier (nn-&gt;writeverf) when this check fails. Every other<br /> durable-storage-failure path in these functions calls<br /> commit_reset_write_verifier() before returning an error.<br /> <br /> The missing rotation means clients holding UNSTABLE write data under the<br /> current verifier will COMMIT, receive the unchanged verifier back, and<br /> conclude their data is durable — silently dropping data that failed<br /> writeback. This violates the UNSTABLE+COMMIT durability contract<br /> (RFC 1813 §3.3.7, RFC 8881 §18.32).<br /> <br /> Add commit_reset_write_verifier() calls at both filemap_check_wb_err()<br /> error sites, matching the pattern used by adjacent error paths in the<br /> same functions. The helper already filters -EAGAIN and -ESTALE<br /> internally, so the calls are unconditionally safe.