The Linux kernel's NFS server functions nfsd_vfs_write() and nfsd_commit() both call filemap_check_wb_err() to detect deferred writeback errors but fail to rotate the server's write verifier (nn->writeverf) when such errors are detected. This omission means clients holding UNSTABLE write data under the current verifier may commit, receive the unchanged verifier, and incorrectly conclude their data is durable, resulting in silent data loss. The fix involves adding commit_reset_write_verifier() calls at the error sites to ensure the write verifier is properly rotated, aligning with the behavior of other durable-storage-failure paths in these functions and maintaining compliance with the UNSTABLE+COMMIT durability contract as specified in RFC 1813 §3.3.7 and RFC 8881 §18.32.

Clients using NFS with the affected Linux kernel may experience silent data loss because the server does not properly reset the write verifier after deferred writeback errors. This causes clients to believe their data has been durably stored when it has not, violating the durability guarantees of the NFS protocol. There is no indication of known exploits in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. The described fix involves adding calls to reset the write verifier on error paths in the Linux kernel NFS server code. Users should monitor official Linux kernel updates and apply patches once available to address this issue.