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 250A8584944 for ; Fri, 11 Sep 2026 19:55:09 +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=1789156515; cv=none; b=SlF0e7FIFJKViK9bNDFh0ijpmHRpixe+MJmNJaZkqlMS/OPixXkgyNTWl85HoE+CflxW5/JjHSMfx5i0dsRwCZD+OoPlZKwXLqkEZ6NP8CcvSdDBrgWBFU5u8Of+3NTPyw/+fPFbDMyxyFsuMrJac2pgIjMPVgjemqw/JKjvXAw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156515; c=relaxed/simple; bh=6ODRuWXIBZZmd7aJ8i4WSZZmjfJod211VxiZmYh4yew=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Y9RdEqk1AcplxnaDF6TK+rVPFR6F3rzPBxI9xKG9hE1wlPhwKiPEA6aC0MMiXa6XPzlB2oObV8wZKymmNn6xQg8pjtuIaaNqZ86nJzA5T0TSDw9dSAWSoRQyROHiwQInL2Yft/OL8e3GHcJay+PwEBV7RZWs5ScW1YHjMrnaAN8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dImLOxuK; 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="dImLOxuK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1EF8E1F000FF; Fri, 11 Sep 2026 19:55:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156506; bh=iCYqs2PS1T4hfnkKp26aPNDU0wea18O3Q1onuytnxoQ=; h=From:To:Cc:Subject:Date:Reply-To; b=dImLOxuKuzKwM8JSmT+kL8xDpt+hswVqr4YUC3A9+alKkor093CvotRxyTYSMtCdf 9WpAmrTNm0W++axSnQTvQlbsiYnLvlU92kiGUgYB4PGM43DBD2Dw9bk0r7boY9Oh3I VmA/HCOcch1SsVZ51PP4rja7ySqlOB1/P+ktuSQM= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89540: sunrpc: init gssp_lock before publishing proc entry Date: Fri, 11 Sep 2026 21:43:49 +0200 Message-ID: <2026091119-CVE-2026-89540-a6ce@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=4570; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=/5Qz7BtnyTztoJ4HHFzYnXn0AKzI26y2hXSlIXBv7Rg=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIuPzAgMNROoV1+6r0TfftWHS1Kl7DictXZZXeaJmM eMj7Sm3O2JZGASZGGTFFFm+bOM5ur/ikKKXoe1pmDmsTCBDGLg4BWAioucYFkxI3syxhMvo5smL See5n8yRUf9gKsQwV4Sd5XvfslOL7tnyzd+y8GXl+jd65gA= 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: sunrpc: init gssp_lock before publishing proc entry create_use_gss_proxy_proc_entry() publishes /proc/net/rpc/use-gss-proxy via proc_create_data() before init_gssp_clnt() runs mutex_init() on sn->gssp_lock. Once the dentry is linked under proc_subdir_lock it is immediately reachable from userspace, so a write that lands in the window drives set_gssp_clnt() into mutex_lock() on a zero-initialized struct mutex. create_use_gss_proxy_proc_entry(net) proc_create_data("use-gss-proxy", ...) /* dentry live */ init_gssp_clnt(sn) mutex_init(&sn->gssp_lock) /* too late */ write_gssp() set_gssp_clnt(net) mutex_lock(&sn->gssp_lock) /* uninitialized */ gssp_rpc_create(...) sn->gssp_clnt = clnt mutex_unlock(&sn->gssp_lock) The window spans only the two statements between proc_create_data() returning and init_gssp_clnt(), so a writer reaches it only if the registering thread is preempted there while another task is already opening the freshly published file. register_pernet_subsys() runs in preemptible context under pernet_ops_rwsem, so that preemption is possible, and the window widens on auth_rpcgss module load, when the proc entry is created for every live net namespace whose tasks are already running. A writer that wins the race locks a zero-filled struct mutex. On CONFIG_DEBUG_MUTEXES the missing magic value trips a "lock used without init" splat; on a production kernel the fast path acquires the lock via CMPXCHG(owner, 0, current). In the latter case a second writer that arrives before init_gssp_clnt() re-zeroes owner can enter set_gssp_clnt() concurrently, shut down the first writer's clnt while it is still in use, and leak the loser's clnt. Fix by initializing sn->gssp_lock in sunrpc_init_net() so its lifetime matches the sunrpc_net it lives in. sn->gssp_clnt is already NULL from the kzalloc that backs net_generic storage, so the lazy helper is no longer needed; drop init_gssp_clnt(), its prototype, and the call from create_use_gss_proxy_proc_entry(). sunrpc.ko is a build-time dependency of auth_rpcgss.ko, so sunrpc_init_net() has always run on every netns before any auth_gss pernet init can publish the proc entry. The Linux kernel CVE team has assigned CVE-2026-89540 to this issue. Affected and fixed versions =========================== Issue introduced in 3.10 with commit 030d794bf49855f5e2a9e8dfbfad34211d1eb08b and fixed in 6.12.109 with commit f15b87521168c2a92cb1931f532cba422f856f01 Issue introduced in 3.10 with commit 030d794bf49855f5e2a9e8dfbfad34211d1eb08b and fixed in 6.18.50 with commit edeefb111d6181a4aa278f415b005efe284b9489 Issue introduced in 3.10 with commit 030d794bf49855f5e2a9e8dfbfad34211d1eb08b and fixed in 7.2.4 with commit 3f019571928b269feebcff59926ec13294215e0e Issue introduced in 3.10 with commit 030d794bf49855f5e2a9e8dfbfad34211d1eb08b and fixed in 7.3-rc1 with commit 5ce1ed6159731a41fdd0b03eedbed4e147036a5a 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-2026-89540 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: net/sunrpc/auth_gss/gss_rpc_upcall.c net/sunrpc/auth_gss/gss_rpc_upcall.h net/sunrpc/auth_gss/svcauth_gss.c net/sunrpc/sunrpc_syms.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/f15b87521168c2a92cb1931f532cba422f856f01 https://git.kernel.org/stable/c/edeefb111d6181a4aa278f415b005efe284b9489 https://git.kernel.org/stable/c/3f019571928b269feebcff59926ec13294215e0e https://git.kernel.org/stable/c/5ce1ed6159731a41fdd0b03eedbed4e147036a5a