linux-kernel - Re: [PATCH] ext4: Fix buffer_head refcnt leak when ext4

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Message-ID: <20200514145415.GU1596452@mit.edu>
Date:   Thu, 14 May 2020 10:54:15 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Xiyu Yang <xiyuyang19@...an.edu.cn>
Cc:     Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        yuanxzhang@...an.edu.cn, kjlu@....edu,
        Xin Tan <tanxin.ctf@...il.com>
Subject: Re: [PATCH] ext4: Fix buffer_head refcnt leak when ext4_iget() fails

On Thu, Apr 23, 2020 at 01:09:27PM +0800, Xiyu Yang wrote:
> ext4_orphan_get() invokes ext4_read_inode_bitmap(), which returns a
> reference of the specified buffer_head object to "bitmap_bh" with
> increased refcnt.
> 
> When ext4_orphan_get() returns, local variable "bitmap_bh" becomes
> invalid, so the refcount should be decreased to keep refcount balanced.
> 
> The reference counting issue happens in one exception handling path of
> ext4_orphan_get(). When ext4_iget() fails, the function forgets to
> decrease the refcnt increased by ext4_read_inode_bitmap(), causing a
> refcnt leak.
> 
> Fix this issue by calling brelse() when ext4_iget() fails.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>

Applied, thanks.

					- Ted