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From: Tejun Heo <tj@kernel.org>
To: gregkh@linuxfoundation.org
Cc: kernel-team@fb.com, linux-kernel@vger.kernel.org,
	cgroups@vger.kernel.org, lizefan@huawei.com, hannes@cmpxchg.org,
	namhyung@kernel.org, ast@kernel.org, daniel@iogearbox.net,
	Tejun Heo <tj@kernel.org>
Subject: [PATCH 05/10] kernfs: kernfs_find_and_get_node_by_ino() should only look up activated nodes
Date: Mon,  4 Nov 2019 15:59:39 -0800	[thread overview]
Message-ID: <20191104235944.3470866-6-tj@kernel.org> (raw)
In-Reply-To: <20191104235944.3470866-1-tj@kernel.org>

kernfs node can be created in two separate steps - allocation and
activation.  This is used to make kernfs nodes visible only after the
internal states attached to the node are fully initialized.
kernfs_find_and_get_node_by_id() currently allows lookups of nodes
which aren't activated yet and thus can expose nodes are which are
still being prepped by kernfs users.

Fix it by disallowing lookups of nodes which aren't activated yet.

kernfs_find_and_get_node_by_ino()

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
---
 fs/kernfs/dir.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 798f0f03b62b..beabb585a7d8 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -714,7 +714,13 @@ struct kernfs_node *kernfs_find_and_get_node_by_ino(struct kernfs_root *root,
 	if (!kn)
 		goto err_unlock;
 
-	if (unlikely(!atomic_inc_not_zero(&kn->count)))
+	/*
+	 * ACTIVATED is protected with kernfs_mutex but it was clear when
+	 * @kn was added to idr and we just wanna see it set.  No need to
+	 * grab kernfs_mutex.
+	 */
+	if (unlikely(!(kn->flags & KERNFS_ACTIVATED) ||
+		     !atomic_inc_not_zero(&kn->count)))
 		goto err_unlock;
 
 	spin_unlock(&kernfs_idr_lock);
-- 
2.17.1


  parent reply	other threads:[~2019-11-05  0:00 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-04 23:59 [PATCHSET cgroup/for-5.5] kernfs,cgroup: support 64bit inos and unify cgroup IDs Tejun Heo
2019-11-04 23:59 ` [PATCH 01/10] kernfs: fix ino wrap-around detection Tejun Heo
2019-11-04 23:59 ` [PATCH 02/10] writeback: use ino_t for inodes in tracepoints Tejun Heo
2019-11-05  9:11   ` Jan Kara
2019-11-04 23:59 ` [PATCH 03/10] netprio: use css ID instead of cgroup ID Tejun Heo
2019-11-05 13:27   ` Neil Horman
2019-11-04 23:59 ` [PATCH 04/10] kernfs: use dumber locking for kernfs_find_and_get_node_by_ino() Tejun Heo
2019-11-04 23:59 ` Tejun Heo [this message]
2019-11-04 23:59 ` [PATCH 06/10] kernfs: convert kernfs_node->id from union kernfs_node_id to u64 Tejun Heo
2019-11-04 23:59 ` [PATCH 07/10] kernfs: combine ino/id lookup functions into kernfs_find_and_get_node_by_id() Tejun Heo
2019-11-04 23:59 ` [PATCH 08/10] kernfs: implement custom exportfs ops and fid type Tejun Heo
2019-11-04 23:59 ` [PATCH 09/10] kernfs: use 64bit inos if ino_t is 64bit Tejun Heo
2019-11-04 23:59 ` [PATCH 10/10] cgroup: use cgrp->kn->id as the cgroup ID Tejun Heo
2019-11-06 13:50 ` [PATCHSET cgroup/for-5.5] kernfs,cgroup: support 64bit inos and unify cgroup IDs Namhyung Kim
2019-11-07 15:31   ` Tejun Heo
2019-11-12 15:51 ` Tejun Heo
2019-11-12 16:08   ` Greg KH
2019-11-12 16:09 ` Greg KH
2019-11-12 16:19   ` Tejun Heo

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