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 5CB4F582B98 for ; Fri, 11 Sep 2026 20:03:44 +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=1789157034; cv=none; b=edD8uZXCMPIde5vzRhnpywq1QzfFIyhf/1B08dM/Hd9O2O4lXg/gA3DAcIgGmuYncLam6Ahx1DuqMLY8YpgC5FarHWmVLje3vLZ/OdHlLvGOhp/19xX0qWnVznfvMmMZTyOrYKoEWzP+Oqp59P69KCcnwS3wtXjYxNOkqxii4Ko= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789157034; c=relaxed/simple; bh=WAoUBzei/1o2nmJmZ6DbphcGFLGj/MPkd570HwGylsk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=fKDrE4LhXRmaBj9uC98Xb9Pdid8ZRlmsdraDjLBtpw8zRIsgklg4KXz74xuf+RdhEvDfi3amMHOyJ1YxrsM9tut0SjKcb07Wg8YkpYQwU0pjBbLv8ruHmuIRftTktN55ha7yiMd5XaeecLeTs2wqcxq9e1W7Pk+QrrJ2UfUWl04= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=iDR8r2EZ; 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="iDR8r2EZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 523C21F0089D; Fri, 11 Sep 2026 20:03:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789157021; bh=cBCFtDcKww49rMD+Ru7/NNvVBwxG3Dju9X66+JPYcEQ=; h=From:To:Cc:Subject:Date:Reply-To; b=iDR8r2EZTSOSd3S0sZLcjyZijcOay4bR7tTYO0D7GWLednXSK4DxzWWChgt5QpjhQ F7NgXG7Zg5NfXA+51vIgDyalLzTpZyRL19P1QYr/VkzG4nMYbY1/5z4/v56kM4R1F7 h0GTnuUjDNNLDK/gZXZcaraHBTQWZWn3bepfo+Uw= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89711: NFSD: remove flawed WARN_ON_ONCE from nfsd_mode_check Date: Fri, 11 Sep 2026 21:46:40 +0200 Message-ID: <2026091158-CVE-2026-89711-221f@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=3045; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=a4jqXVsyaQFuerKQW4HBJSOn7ijIKZ2Lrvj5LLVsdIo=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLItvSOB3fK0yZveGz65GC9T0xeZ0zTOXTPvPd2V+Wp BCe2pDdEcvCIMjEICumyPJlG8/R/RWHFL0MbU/DzGFlAhnCwMUpABP59I9hQd/in6ZChkEbNOZn dWzi0Ahu8ZG2YZgr4yTe1f/XTm39HZmDuyJPxJVej3sJAA== 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: remove flawed WARN_ON_ONCE from nfsd_mode_check The header for commit e75b23f9e323 ("nfsd: check d_can_lookup in fh_verify of directories") details the assumption that justified adding the WARN_ON_ONCE to nfsd_mode_check(), that assumption is invalid (in the case of NFS reexport). When NFSD exports an NFS filesystem it is very possible for nfsd_mode_check() to encounter a @dentry that doesn't have i_op->lookup (see nfs_fhget()'s NFS_ATTR_FATTR_MOUNTPOINT and NFS_ATTR_FATTR_V4_REFERRAL handling, and d_flags_for_inode()). So remove nfsd_mode_check()'s WARN_ON_ONCE(). The nfserr_notdir return on that branch must stay. It guards the subsequent lookup_one_unlocked() -> __lookup_slow() path, which calls inode->i_op->lookup() with no NULL check, so returning nfserr_notdir is what keeps a client LOOKUP into such a @dentry from dereferencing a NULL method pointer. The Linux kernel CVE team has assigned CVE-2026-89711 to this issue. Affected and fixed versions =========================== Issue introduced in 4.8 with commit e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c and fixed in 6.12.109 with commit b55b4d880bb080fa10eb08ba21a5d8679b8102fe Issue introduced in 4.8 with commit e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c and fixed in 6.18.50 with commit 7ef182a8fe9c12b0d936880b1e504840639aa009 Issue introduced in 4.8 with commit e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c and fixed in 7.2.4 with commit a275de3bac5635514ca830f2e46b5ff0e66b5c4c Issue introduced in 4.8 with commit e75b23f9e323b1e0759619c39d5a9f7a3a5d9d2c and fixed in 7.3-rc1 with commit aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e 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-2026-89711 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/nfsfh.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/b55b4d880bb080fa10eb08ba21a5d8679b8102fe https://git.kernel.org/stable/c/7ef182a8fe9c12b0d936880b1e504840639aa009 https://git.kernel.org/stable/c/a275de3bac5635514ca830f2e46b5ff0e66b5c4c https://git.kernel.org/stable/c/aa0cf48a448c5a9fe1a1e880899ecd589ce39e6e