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From:   Muchun Song <songmuchun@bytedance.com>
To:     gregkh@linuxfoundation.org, tj@kernel.org
Cc:     linux-kernel@vger.kernel.org, muchun.song@linux.dev,
        Muchun Song <songmuchun@bytedance.com>
Subject: [PATCH] kernfs: fix missing kernfs_idr_lock to remove an ID from the IDR
Date:   Tue, 16 May 2023 11:45:36 +0800
Message-Id: <20230516034536.25548-1-songmuchun@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The root->ino_idr is supposed to be protected by kernfs_idr_lock, fix
it.

Fixes: 488dee96bb62 ("kernfs: allow creating kernfs objects with arbitrary uid/gid")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 fs/kernfs/dir.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 45b6919903e6..84a2cd196076 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -525,6 +525,13 @@ void kernfs_get(struct kernfs_node *kn)
 }
 EXPORT_SYMBOL_GPL(kernfs_get);
 
+static void kernfs_idr_remove(struct kernfs_root *root, struct kernfs_node *kn)
+{
+	spin_lock(&kernfs_idr_lock);
+	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
+	spin_unlock(&kernfs_idr_lock);
+}
+
 /**
  * kernfs_put - put a reference count on a kernfs_node
  * @kn: the target kernfs_node
@@ -559,9 +566,7 @@ void kernfs_put(struct kernfs_node *kn)
 		simple_xattrs_free(&kn->iattr->xattrs);
 		kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
 	}
-	spin_lock(&kernfs_idr_lock);
-	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
-	spin_unlock(&kernfs_idr_lock);
+	kernfs_idr_remove(root, kn);
 	kmem_cache_free(kernfs_node_cache, kn);
 
 	kn = parent;
@@ -655,7 +660,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 	return kn;
 
  err_out3:
-	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
+	kernfs_idr_remove(root, kn);
  err_out2:
 	kmem_cache_free(kernfs_node_cache, kn);
  err_out1:
-- 
2.11.0