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 00A9B58F067 for ; Fri, 11 Sep 2026 20:01:19 +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=1789156888; cv=none; b=HMxd9S7ZnSEZTopLqF1FqOAUSa2AbjVLwzrEsPvIrZL9q3ivh6pdq2ofTBGjqhNUrBXrU8M4m8c/ngTXzn2l4KM/TW3p5LHKq30pss6CjNTSoK1BVyp2zU5BIV848hWnsYUfkZl9Kg8bC4ssm/b3DOUh2rd15dJmOq1AjkZ7pes= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156888; c=relaxed/simple; bh=uOhP4CWUtC/Eij/ohSGYSyrAC8c6gVt4CWV4hm/Yjr0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=moZhS+mH0Zc0NKPngcZVT0VDwStHIjyQd3uNAvXt7NKsA5c945jOD0XdWuAKv9kLjpcN5WbEcrM1WCEDw/u7MXPo0oqIFbNin0Y5O6sDKx/nQP5h5eUpt4NgrB5VCr9DSbWv+uGlkxu86Q6QRoYSQIqVaIn8ANyCQFxBkvlEiKA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=P81H+4i0; 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="P81H+4i0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3260B1F0089B; Fri, 11 Sep 2026 20:01:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156877; bh=/R31Ljj+oksaW5ZxY4UwioNyrVLQ1qjSkDuSM5sfpz4=; h=From:To:Cc:Subject:Date:Reply-To; b=P81H+4i0dkmqKxDU31tGuKxuea31lVrmCmF31TpmKKYnHgRowJxFEHTDqU4LEwHNI prPzCpXXousvElPZgXNMzZF1HXTFLP4lFYvA4ZBoeylyueb9uharHTNUwiqbTfbQwb YZRcHQmMNkhJq/Wt3PVPl+Lten1s33SGeOHM2nKM= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89661: NFSD: Prevent post-shutdown use-after-free in unlock_filesystem Date: Fri, 11 Sep 2026 21:45:50 +0200 Message-ID: <2026091146-CVE-2026-89661-aae3@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=2797; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=dkBBNGyMaXOlVKMuhbAe1GHI49cQnp8E2uPdhoKfx3w=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIqs+7A7gZfz9a1p7yvMPGjNSft1vMZ0SeWr6//sxe iX/BF587IhlYRBkYpAVU2T5so3n6P6KQ4pehranYeawMoEMYeDiFICJ+GYzLNjz8I9Tnm5Q1PzI poiT7W3sCprd2xgW9H3SmsGn/C18X4TmT7nGHU0/ObwiAQ== 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: Prevent post-shutdown use-after-free in unlock_filesystem Writing a filesystem path to /proc/fs/nfsd/unlock_filesystem runs nfsd4_cancel_copy_by_sb() before nfsd_mutex is held and before the handler confirms that nn->nfsd_serv is set. Once nfsd has shut down, nfs4_state_destroy_net() has freed nn->conf_id_hashtbl but left the pointer intact, so the cancel helper iterates freed slab memory as an array of struct list_head and then dereferences a bogus nfs4_client when it takes clp->async_lock. A local administrator holding CAP_SYS_ADMIN can reach this use-after-free by stopping the server and then writing to unlock_filesystem; KASAN reports a slab-use-after-free read in nfsd4_cancel_copy_by_sb(). nfsd4_revoke_states() walks the same state tables and for that reason already runs only under nfsd_mutex with nn->nfsd_serv confirmed present. Move the async COPY cancel into that protected section so every NFSv4 state-table walker on this path observes a running server. Async copies exist only while the server runs, so gating the cancel on nn->nfsd_serv loses nothing. The Linux kernel CVE team has assigned CVE-2026-89661 to this issue. Affected and fixed versions =========================== Issue introduced in 7.0 with commit 3daab3112f039cf849f96764019b096bb0a39d04 and fixed in 7.2.4 with commit 0c1a755b7212e0835398d4df5e782ea85ccd7476 Issue introduced in 7.0 with commit 3daab3112f039cf849f96764019b096bb0a39d04 and fixed in 7.3-rc1 with commit 292d915d3ba6fd15eeb88351fa10581683073109 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-2026-89661 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/nfsctl.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/0c1a755b7212e0835398d4df5e782ea85ccd7476 https://git.kernel.org/stable/c/292d915d3ba6fd15eeb88351fa10581683073109