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 7DCBB30C366; Fri, 4 Sep 2026 06:07:45 +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=1788502066; cv=none; b=fYQDUlfUjc+wrHtdI69V2j3GE2CTem1KD/yVlDYJ+VES0RSIn7nXN3XU6qBFHhRK+8nfiMYr1yip9RPyTCaEf7lMytdUtu9sg0DolQhsdRAkihPDlPiwE5mr1pTsIEU1xU7FYdwuxxv/no1F3IC2OgUhYov8kuF0EJ9fSOK8A+M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788502066; c=relaxed/simple; bh=MhMrSW7f1Mnu+ZpVXK5lqIDG697VzPnuqJQvrFPcg9Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nr+BGImeclnP8V7vET1vMgiRIWrdOkPqAivorHeZtAqkkFUobdDzoD1bIJC+n2xVdXT1NVJoAfVuZCCp2MmIPNZqeh72E+0/u2qoDRy9/UIZeLFXjJHGe2z/p9NSnIMxku/nmBmrR/O/FSLx4mEFV0y/JPOhCeR1+hESBDiZ+Pg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=oqnD/lll; 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="oqnD/lll" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF28D1F00A3D; Fri, 4 Sep 2026 06:07:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788502065; bh=VxI5LgZZv3MPSEAcDWFAIcdIiz5Gqnu4xFNkHN5NxCM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=oqnD/lll1fKHqVYvpo70tCd3+fCjrXAzY4OpX/jhzk2DxUNvt4p+TBSkR8pGhF+Sj Z4jZE3t25Snma6hSdGWTPrDyjqud/PM8yrLM8FUkveC5lbJG0X8N85EJYR0BqcPIPz 1vIyGQTOA4F3z857NyukS+LWgE8vTnflKsZa16Vw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , Chuck Lever Subject: [PATCH 6.12 076/403] nfsd: release path refs on follow_down() error Date: Fri, 4 Sep 2026 06:57:59 +0200 Message-ID: <20260904045736.562406809@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045734.806166532@linuxfoundation.org> References: <20260904045734.806166532@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 6.12-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 @@ -133,8 +133,10 @@ 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 */