From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9C3B758FD22 for ; Fri, 11 Sep 2026 20:05:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789157118; cv=none; b=Pp2ekcIwaS+3aM0KtpZLIZtfNdOSZBFki1j6wdDQoqed6jz8RA7z2MYQ47UGZ3q64L4Z+NSb+C6HsalPx1SDR619cuYZcShrP/TL63+vDQYtxCTpnDyzkCL6vRc34z/8UAxMsmjvwqwjKwkUTvGArc9ZMpk4mdNZvrkEyn/LDJM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789157118; c=relaxed/simple; bh=CLNVeTjVi+sISNCTt3r6WmdL3KLV9ELiU3nz/lnII5Q=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=R6CwOLRvQjdA6N6SplfSgtDWQU/v49nUxnELZmI/ezRi2KrkLdi+czCWQYZRLJG2Yqzh/xtJT7Wi2v6Gz8CwXcgvXCTc8pp1EJWMjJdBk35ocPofmpmP7KYMgPEbup3PyVT2hczg+cXXpPHDh5IMTZNsCWUsJ9FfzFXmqdDmIgA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QxsGDHTc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="QxsGDHTc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10A8E1F000FF; Fri, 11 Sep 2026 20:05:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789157111; bh=EvPHJlhtCatP2VGgUmNppHI8/KgEvN0H4stVdAM/mQI=; h=From:To:Cc:Subject:Date:Reply-To; b=QxsGDHTcf5I9PquKtA4iDQRvE0PlBM9HscwUC4xa2AwaWbkJFxWzdWsOs7ttsQ2dw U9oJvZrqGEIKeI2RuxPIy7uel/8RDwaIBtIUPytgVXqhWvNUA6HtbU2lt4Jtje1zRT zFnsLtAmuIPgW/zW59BrQ6yoldWIQegEpRR/pYGk= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89706: nfsd: Reset write verifier when async COPY writeback fails Date: Fri, 11 Sep 2026 21:46:35 +0200 Message-ID: <2026091157-CVE-2026-89706-d764@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3627; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=+PzqNQJd/cZd9wVcdeWhNQ/ZBU+nMNtr87znp+fBLKk=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIlsl/r87/mFbZqBYfOwCvzLPtkX5MjU1ZQsCT9e8Z qqdOH1hRywLgyATg6yYIsuXbTxH91ccUvQytD0NM4eVCWQIAxenAEyE5zPD/IRTi8Ny81vWfpBc vHJe3P0H9h0Mkxnm6Ut9TxJ/3J990vFmbmaQ4HvB2igbAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: nfsd: Reset write verifier when async COPY writeback fails Async COPY captures nn->writeverf at request time and reports it to the client via CB_OFFLOAD after the worker kthread completes. When the post-copy vfs_fsync_range() or filemap_check_wb_err() in _nfsd_copy_file_range() reports an error, the worker correctly leaves NFSD4_COPY_F_COMMITTED clear so that CB_OFFLOAD encodes wr_stable_how as NFS_UNSTABLE, but the server's write verifier is not rotated. A client that receives NFS_UNSTABLE in CB_OFFLOAD follows up with COMMIT to make the copied data durable. With the verifier unchanged, COMMIT returns the same value the client just received via CB_OFFLOAD, and the client concludes the copy is durable -- silently dropping the data whose writeback in fact failed. This violates the UNSTABLE+COMMIT durability contract (RFC 7862 section 15.1, RFC 8881 section 18.32) and matches the bug just fixed in nfsd_vfs_write() and nfsd_commit(). Rotate nn->writeverf at the writeback-failure site. The async COPY worker has no svc_rqst, so commit_reset_write_verifier() is not available here; calling nfsd_reset_write_verifier() directly mirrors the trace-less reset already used by nfsd_file_check_write_error() for the same purpose. Filter out -EAGAIN and -ESTALE, matching commit_reset_write_verifier(), since neither indicates a durable-storage failure. The Linux kernel CVE team has assigned CVE-2026-89706 to this issue. Affected and fixed versions =========================== Issue introduced in 5.14 with commit eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and fixed in 6.12.109 with commit 31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0 Issue introduced in 5.14 with commit eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and fixed in 6.18.50 with commit 591134e059e3456180244a826d6917cdc183140b Issue introduced in 5.14 with commit eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and fixed in 7.2.4 with commit bf0cd31a9abcb728c17d79b4c2cc533612a8b6af Issue introduced in 5.14 with commit eac0b17a77fbd763d305a5eaa4fd1119e5a0fe0d and fixed in 7.3-rc1 with commit f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9 Issue introduced in 5.10.220 with commit 817c6eb975798647c4bbbfc9eb288aa413ec7f65 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-89706 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/nfsd/nfs4proc.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/31d4d0a62ec4bafbcdbad142f11ab1f90794b1d0 https://git.kernel.org/stable/c/591134e059e3456180244a826d6917cdc183140b https://git.kernel.org/stable/c/bf0cd31a9abcb728c17d79b4c2cc533612a8b6af https://git.kernel.org/stable/c/f5cb2276954cb80987a93ef9f9dfbfdbfc0f10b9