linux-kernel - Re: [PATCH v2] btrfs: Fix block group leak when remove it fails

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Message-ID: <20200422225054.GU18421@twin.jikos.cz>
Date:   Thu, 23 Apr 2020 00:50:54 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Xiyu Yang <xiyuyang19@...an.edu.cn>
Cc:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, yuanxzhang@...an.edu.cn,
        kjlu@....edu, Xin Tan <tanxin.ctf@...il.com>
Subject: Re: [PATCH v2] btrfs: Fix block group leak when remove it fails

On Tue, Apr 21, 2020 at 10:54:11AM +0800, Xiyu Yang wrote:
> btrfs_remove_block_group() invokes btrfs_lookup_block_group(), which
> returns a local reference of the blcok group that contains the given
> bytenr to "block_group" with increased refcount.
> 
> When btrfs_remove_block_group() returns, "block_group" becomes invalid,
> so the refcount should be decreased to keep refcount balanced.
> 
> The reference counting issue happens in several exception handling paths
> of btrfs_remove_block_group(). When those error scenarios occur such as
> btrfs_alloc_path() returns NULL, the function forgets to decrease its
> refcnt increased by btrfs_lookup_block_group() and will cause a refcnt
> leak.
> 
> Fix this issue by jumping to "out_put_group" label and calling
> btrfs_put_block_group() when those error scenarios occur.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>

Added to misc-next, thanks.