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 0B9D53264D6 for ; Sat, 5 Sep 2026 01:50:12 +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=1788573014; cv=none; b=NunFib56gz3CTphm/2VZ7ja9zl+p9fNHhwuJr7oQN/Z3nHGrPK6ptxT50VCQhpIWAksxmue1QWh8oWOLYG6i60dP94K3UrqOHxHs3b3gxhZD4OZJsvUkOCIqnW3nC77PQGkcsHDSGZjhrD6XgL9PRqLLzb7DBoCSWED4EGc/9c8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788573014; c=relaxed/simple; bh=29Q7XMq0U5wnPa5D64rHbtUIN4EnnJGwyAeuJitAZx8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=e/Zmz/4PQ+I5C0D8t/6wFRVz5wq9lARt2Tqnfb3qAgq8MAzw+VskTuPVhyullqpZOKfTqnrL4owFVJ7yYqmdGSgIgD6mQjL2R78xybHzhxMw2T/9Fu2i7qiuawGCl18Cm8ULnw8vZt94xbN3PHZkh2dNo9X8dAnDbEEnRzq4ypU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=e5T3WO9C; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="e5T3WO9C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 30ED91F00A3D; Sat, 5 Sep 2026 01:50:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788573012; bh=IlcJo4LfOPE8CDvTAoHGiiN2sLIEa9kgMljoHpKhppQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=e5T3WO9CANROJQdIz4jdTzb3unuYtO5JCtT4NPcpISKWvWF9Qm850mJ5FooDhtYXV t5M+Oy1E0r0C0bHrhDkSRCFN/wcUYVI+KHiE9qWA7it8qbOznNmJU9TmXKesCCmysw WSH6dB0ALzJpG5stUpw4b7N28+rjyGgN3TyhoZSMNotEpxvG4AoYW7SaAkdaDCsJDD 4Y1c1xCVz1GTP1D5hPV0JeKdZup+JkYrXaGSl4bmsqAZytAxbAsdkF3XI9aOudF5zR uM/cPXOqPX55wIfBqBDYvqwYReEKN1JGjiQMJmMkxoENbfPQTXXfnVIvc6x9Xezpd/ BbKXud4mNXawA== From: Sasha Levin To: stable@vger.kernel.org Cc: Chris Mason , Chuck Lever , Sasha Levin Subject: [PATCH 5.10.y] nfsd: release path refs on follow_down() error Date: Fri, 4 Sep 2026 21:50:10 -0400 Message-ID: <20260905015010.1807085-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090325-landless-renovate-1b8b@gregkh> References: <2026090325-landless-renovate-1b8b@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chris Mason [ Upstream commit 6cba08dc1922140d260cfeb30bbda4ee1bf869d8 ] nfsd_cross_mnt() initializes a local struct path with mntget() and dget() before calling follow_down(). On a negative return the error arm jumps to out without releasing those references: err = follow_down(&path, follow_flags); if (err < 0) goto out; follow_down() never drops the caller's entry-time refs on any error sub-case; for example a pre-cross d_manage() failure leaves path untouched, so the mntget()/dget() taken on entry survive the call. Every other early-exit arm in nfsd_cross_mnt() (other-namespace return, IS_ERR(exp2), and the success tail after the swap) already calls path_put(&path); the err < 0 arm is the lone omission. The leak inflates mnt_count and d_count on each failed cross-mount, blocking umount and pinning dentries against the shrinker, and is reachable by any authenticated NFS client through nfsd_lookup_dentry or the NFSv4 READDIR encode path. Fix by calling path_put(&path) before the goto out in the err < 0 arm so the entry-time refs are released on all follow_down() error returns. Fixes: cc53ce53c869 ("Add a dentry op to allow processes to be held during pathwalk transit") Cc: stable@vger.kernel.org Assisted-by: kres:claude-opus-4-7 Signed-off-by: Chris Mason Link: https://patch.msgid.link/20260531-nfsd-testing-v1-2-7bfa481b0540@kernel.org Signed-off-by: Chuck Lever [ retained the older single-argument follow_down(&path) API ] Signed-off-by: Sasha Levin --- fs/nfsd/vfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index c8eebd03784a2..7aa2338539af9 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -129,8 +129,10 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp, int err = 0; err = follow_down(&path); - if (err < 0) + if (err < 0) { + path_put(&path); goto out; + } if (path.mnt == exp->ex_path.mnt && path.dentry == dentry && nfsd_mountpoint(dentry, exp) == 2) { /* This is only a mountpoint in some other namespace */ -- 2.53.0