CVE-2026-53393

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

nfsd: reset write verifier on deferred writeback errors

nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to

detect deferred writeback errors, but neither rotates the server's write

verifier (nn->writeverf) when this check fails. Every other

durable-storage-failure path in these functions calls

commit_reset_write_verifier() before returning an error.

The missing rotation means clients holding UNSTABLE write data under the

current verifier will COMMIT, receive the unchanged verifier back, and

conclude their data is durable — silently dropping data that failed

writeback. This violates the UNSTABLE+COMMIT durability contract

(RFC 1813 §3.3.7, RFC 8881 §18.32).

Add commit_reset_write_verifier() calls at both filemap_check_wb_err()

error sites, matching the pattern used by adjacent error paths in the

same functions. The helper already filters -EAGAIN and -ESTALE

internally, so the calls are unconditionally safe.