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 D643E42F718 for ; Fri, 11 Sep 2026 20:05:09 +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=1789157114; cv=none; b=JduWE//Tt/qVl4XkCT/IYqsfKJQN6HogOnTYSPpYP8uGvzlC0c/hrZSOtoo2gw9+A43xsHpt/Mkl2/nGmUKBaIkpHRY8jUS5YEvrhP+9zp5k+5LFEY9El2TA3rFmdHhaXnKQwY8oHU0BrGqju0bCqz56TZM7s96xlUbNoqjA3uA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789157114; c=relaxed/simple; bh=wDSXJzEa5T72zve+TF1Cy+3ykByxdm0h1cIFCtWKGOo=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=hoIL4R74md2HkFqNvvvuk6nkbvLb6+kbj76mw/gEUwjETxnj3ACBuxip5ZReCfWFf+TRqoPtATETjuKI40gfjGSrDU/df3jXViHa0SFf5UDEQfNu2Afxj/nUXFyPX/LEuWs2Y1xacGtkAzf9NugEgQ7HQpaNkzReEWxqm478ZhM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=DL43qsPJ; 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="DL43qsPJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C5AB1F00893; Fri, 11 Sep 2026 20:05:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789157105; bh=nonMhMQcXnU6EpqnKkafEfh2MipzkCvvIJaVHkoPXfc=; h=From:To:Cc:Subject:Date:Reply-To; b=DL43qsPJ3z9cU04Z1AHcg73GVEVDFH63L0ECNlMoohfOkRArq4B2mQeuvmUFfAvwV 0HI3P+GdFStnqNLNSDnWqvJhcefsDIkgu0kqFdZJyniqfF13dF1qdQdbVAzsytPe8E N2CTS+3LfosfEI8S111QNFysPYeQtCrabdUWme+I= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89704: nfsd: sample writeback error cursor before async COPY loop Date: Fri, 11 Sep 2026 21:46:33 +0200 Message-ID: <2026091156-CVE-2026-89704-414e@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=3602; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=lD1rD0S0t3qg8kKD+zBILKyRivrPII1r50om2DzR0uc=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIlueGfkec1nYMW++7cT/PS6eDTnLq6+b1u+1TNzvf ObKC8bqjlgWBkEmBlkxRZYv23iO7q84pOhlaHsaZg4rE8gQBi5OAZjIutcM80vSrmRkMbZsyH9x zmrup9ajf09+WM8wz575k2bCF/+kD0a2t3cfL69I53K8BQA= 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: sample writeback error cursor before async COPY loop _nfsd_copy_file_range() samples dst->f_wb_err into "since" after the copy loop, then uses it to detect writeback errors via filemap_check_wb_err() once vfs_fsync_range() returns. Because the nfsd_file cache reuses a single struct file across requests targeting the same inode, a concurrent COMMIT or stable WRITE on dst advances dst->f_wb_err to the current mapping->wb_err via file_check_and_advance_wb_err() during its own vfs_fsync_range(). If that advancement lands between the writeback error appearing in mapping->wb_err and the COPY worker sampling "since", the worker captures the already-advanced cursor, errseq_check() sees cur == since and returns zero, and NFSD4_COPY_F_COMMITTED is set even though writeback failed. CB_OFFLOAD then encodes wr_stable_how = FILE_SYNC4, the client treats the copied data as durable, and the failure becomes silent data loss. Sample since once at the start of the function. The cursor then reflects state in effect before this COPY issues any writes, and filemap_check_wb_err() detects any error that occurs during the copy regardless of which thread first observes it. This matches the pattern used by nfsd_vfs_write() and nfsd4_clone_file_range(). The Linux kernel CVE team has assigned CVE-2026-89704 to this issue. Affected and fixed versions =========================== Issue introduced in 5.17 with commit 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb and fixed in 6.12.109 with commit 52b2db7a72e19ac2686fa4b2a52406661e7bf9e2 Issue introduced in 5.17 with commit 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb and fixed in 6.18.50 with commit 8277d4a11ae2cb5495842be558fd946032c24363 Issue introduced in 5.17 with commit 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb and fixed in 7.2.4 with commit a1cbafe756cd5e6ab0e099062f37da7a5b081169 Issue introduced in 5.17 with commit 555dbf1a9aac6d3150c8b52fa35f768a692f4eeb and fixed in 7.3-rc1 with commit 20a67a7d18221af736f124770c2c5e859b479046 Issue introduced in 5.10.124 with commit f14816f2f928c560d28ba344af689f56efcd6f55 Issue introduced in 5.15.49 with commit 3145fe0ebb16e1715ad541a301bc6675c8375fcd 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-2026-89704 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/52b2db7a72e19ac2686fa4b2a52406661e7bf9e2 https://git.kernel.org/stable/c/8277d4a11ae2cb5495842be558fd946032c24363 https://git.kernel.org/stable/c/a1cbafe756cd5e6ab0e099062f37da7a5b081169 https://git.kernel.org/stable/c/20a67a7d18221af736f124770c2c5e859b479046