linux-kernel - Re: [PATCH] btrfs: Fix refcnt leak in btrfs_recover

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Message-ID: <CAL3q7H4hoSF6=S_ZqTCiKNed0NkFymemGZh4vrRNQ3Nrf9xwkA@mail.gmail.com>
Date:   Mon, 20 Apr 2020 18:34:07 +0100
From:   Filipe Manana <fdmanana@...il.com>
To:     Xiyu Yang <xiyuyang19@...an.edu.cn>
Cc:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, Jeff Mahoney <jeffm@...e.com>,
        linux-btrfs <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] btrfs: Fix refcnt leak in btrfs_recover_relocation

On Mon, Apr 20, 2020 at 6:50 AM Xiyu Yang <xiyuyang19@...an.edu.cn> wrote:
>
> btrfs_recover_relocation() invokes btrfs_join_transaction(), which joins
> a btrfs_trans_handle object into transactions and returns a reference of
> it with increased refcount to "trans".
>
> When btrfs_recover_relocation() returns, "trans" becomes invalid, so the
> refcount should be decreased to keep refcount balanced.
>
> The reference counting issue happens in one exception handling path of
> btrfs_recover_relocation(). When read_fs_root() failed, the refcnt
> increased by btrfs_join_transaction() is not decreased, causing a refcnt
> leak.
>
> Fix this issue by calling btrfs_end_transaction() on this error path
> when read_fs_root() failed.
>
> Fixes: 79787eaab461 ("btrfs: replace many BUG_ONs with proper error
> handling")
> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>

Reviewed-by: Filipe Manana <fdmanana@...e.com>

Looks good, thanks.

> ---
>  fs/btrfs/relocation.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 995d4b8b1cfd..46a451594c7a 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -4606,6 +4606,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
>                 if (IS_ERR(fs_root)) {
>                         err = PTR_ERR(fs_root);
>                         list_add_tail(&reloc_root->root_list, &reloc_roots);
> +                       btrfs_end_transaction(trans);
>                         goto out_free;
>                 }
>
> --
> 2.7.4
>


-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”