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Date:   Wed, 25 Mar 2020 08:50:14 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH v2 3/5] f2fs: fix to avoid NULL pointer dereference
Message-ID: <20200325155014.GB65658@google.com>
References: <20200325091811.60725-1-yuchao0@huawei.com>
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Hi Chao,

I don't want to rebase old commit at this moment, so applied on top of the tree.

Thanks,

On 03/25, Chao Yu wrote:
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> PC is at f2fs_free_dic+0x60/0x2c8
> LR is at f2fs_decompress_pages+0x3c4/0x3e8
> f2fs_free_dic+0x60/0x2c8
> f2fs_decompress_pages+0x3c4/0x3e8
> __read_end_io+0x78/0x19c
> f2fs_post_read_work+0x6c/0x94
> process_one_work+0x210/0x48c
> worker_thread+0x2e8/0x44c
> kthread+0x110/0x120
> ret_from_fork+0x10/0x18
> 
> In f2fs_free_dic(), we can not use f2fs_put_page(,1) to release dic->tpages[i],
> as the page's mapping is NULL.
> 
> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> ---
> v2:
> - fix to skip release tpages[i] if it is NULL in error path.
>  fs/f2fs/compress.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index ef7dd04312fe..6e10800729b6 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -1137,7 +1137,10 @@ void f2fs_free_dic(struct decompress_io_ctx *dic)
>  		for (i = 0; i < dic->cluster_size; i++) {
>  			if (dic->rpages[i])
>  				continue;
> -			f2fs_put_page(dic->tpages[i], 1);
> +			if (!dic->tpages[i])
> +				continue;
> +			unlock_page(dic->tpages[i]);
> +			put_page(dic->tpages[i]);
>  		}
>  		kfree(dic->tpages);
>  	}
> -- 
> 2.18.0.rc1