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 973DE2475E3 for ; Sat, 5 Sep 2026 01:06:23 +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=1788570384; cv=none; b=hu1hCNhVuUSTbOYfUr9RTtph+hswyZd66dMzcbcRVY0qzBYEFicszen5pex4bQZpAzCzAWLii2v2YaSk4Bk8fuJ8eOxfUwyTgbqFPsG4heTjCDT0PTKBm1h3vaHqNVYMzBzZdf5OCgMyKMdrKCiFtL+HUvRZ64LbE7NLMVyBkGw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788570384; c=relaxed/simple; bh=rGNJFmONYnP4evgnIKDRp4GgOWG8KdxYHCOcagaQpeQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Pw4+fmOmtJqtc16Wh3sawREa3fM9bkprXm0tBFbvgR9dImFJqziIh5EYwza9XFn2xLNDsDLrELr0uGZZcfah/Mop5M+DwQZO8UdYvOIZKj2YFO0ZCIaxiT3MttKZuz9dCdyiV2KY8Ksnc0lONEpJfPZVMYt+Aym+Z6q0MZguAZ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=APTjrmKv; 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="APTjrmKv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A21461F00A3D; Sat, 5 Sep 2026 01:06:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788570383; bh=SjmxzkMGvMmy6BZGNCW9GN1tsiA9Pq5zPb2HQNxJ1XI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=APTjrmKvQ+9MkK35OgtUxUab1FFSYYkS6Ypi1+5fZFWCsynj8fCzgBBYFQ8d9VUwG G2giECD3erNuIsDZGSv+is1X31fN5wRFyw+ONFVBxovS/e9yB0x2Q74yRFjXnefxV4 D4k/qSXAyYgVN+1dkzWLQBErB8x38GxLf2OQrIv5e/YftTHYeMXyyWuGPBSgdM5cQm Lc9cbnNzAaCrrTtpxZ0Z6FTcErS7GawupR9ymNv1TsS3Db/gBLMf6EGe/0luEKt8ml 97dRUfAmR29xu/Dzxw9I1gc44erjBQyhWENdC6FV7E80Cd+sr5POu9huDbvo9mfcjK c8TgzuJx9F4zA== From: Sasha Levin To: stable@vger.kernel.org Cc: Chris Mason , Chuck Lever , Sasha Levin Subject: [PATCH 5.15.y] nfsd: release path refs on follow_down() error Date: Fri, 4 Sep 2026 21:06:20 -0400 Message-ID: <20260905010620.1765626-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026090324-reprogram-throwaway-926d@gregkh> References: <2026090324-reprogram-throwaway-926d@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 7b0bc4507ad04..225916fc0c8d3 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