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 9EEC12AD37; Fri, 4 Sep 2026 05:43:06 +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=1788500587; cv=none; b=OFCZvc05rGLrvZEPin+pK5pe1a9P7IEHfnL4W3aBnNL+4w67oWA57O4YiUpSuB71F8g4DvzSDnlDKC61Qmh6RBfMYWFdEC35p7if/iO1H522ileQy/YWeO+HGQeLKgfYn7+KQrphygOdvoMVs0k9uLSVqYXXZ3juUpKgSekUrqo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788500587; c=relaxed/simple; bh=LTUO48e0jiOlr2xJOqv4Ald838SMaXhX3wy9wuvKwrc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kMSizfgAPaOK/QILc5H4yh7I9hosUe319kDElYx+zeN9PVXTX8D5Ue5rlZcVICqnAMF3m0tH5mtYsKhJV+o4O7NaaXReda1ccaM7/cW2TjEONRL/+mmOK3Eh0s1RfjGIuhhk5qLjR4qdnP4ZXdoeRMKDBlA5U1CMouDX4k3UVzY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NunXM8YY; 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="NunXM8YY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 03F4B1F00A3D; Fri, 4 Sep 2026 05:43:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788500586; bh=wf+wyEt7tEC30KGSlOBZo0wcsohm/C74ZltSooHQ1Mg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NunXM8YYbGuS6oEsPEJCjXNf+1nvZPaOC+1NqATlLaQYw8e1vSbJrrgjoBkeBpQk9 G5UwWyx7zKXsG9B9PzdHtjHMFFJ1IqOEM6zbeX8cUjtA5T3WBo9njbGy/Yso7iNFvY 5Mwymt3bs/bjhJlsGHjo1ewOMxtiaRu1g6TZIoQw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , Chuck Lever Subject: [PATCH 6.18 108/552] nfsd: release path refs on follow_down() error Date: Fri, 4 Sep 2026 06:54:25 +0200 Message-ID: <20260904045750.356082760@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason commit 6cba08dc1922140d260cfeb30bbda4ee1bf869d8 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/vfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -136,8 +136,10 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, s follow_flags = LOOKUP_AUTOMOUNT; err = follow_down(&path, follow_flags); - 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 */