linux-kernel - [PATCH 5.6 031/126] configfs: fix config_item refcnt leak in configfs

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Message-Id: <20200526183940.415664108@linuxfoundation.org>
Date:   Tue, 26 May 2020 20:52:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>, Christoph Hellwig <hch@....de>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.6 031/126] configfs: fix config_item refcnt leak in configfs_rmdir()

From: Xiyu Yang <xiyuyang19@...an.edu.cn>

[ Upstream commit 8aebfffacfa379ba400da573a5bf9e49634e38cb ]

configfs_rmdir() invokes configfs_get_config_item(), which returns a
reference of the specified config_item object to "parent_item" with
increased refcnt.

When configfs_rmdir() returns, local variable "parent_item" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
configfs_rmdir(). When down_write_killable() fails, the function forgets
to decrease the refcnt increased by configfs_get_config_item(), causing
a refcnt leak.

Fix this issue by calling config_item_put() when down_write_killable()
fails.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Signed-off-by: Christoph Hellwig <hch@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/configfs/dir.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index cf7b7e1d5bd7..cb733652ecca 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -1519,6 +1519,7 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
 		spin_lock(&configfs_dirent_lock);
 		configfs_detach_rollback(dentry);
 		spin_unlock(&configfs_dirent_lock);
+		config_item_put(parent_item);
 		return -EINTR;
 	}
 	frag->frag_dead = true;
-- 
2.25.1