RE: [PATCH] f2fs: do not allow to decompress files have FI_COMPRESS_RELEASED

["Sungjong Seo" <sj1557.seo@samsung.com>]

> If a file has FI_COMPRESS_RELEASED, all writes for it should not be
> allowed. However, as of now, in case of compress_mode=user, writes
> triggered by IOCTLs like F2FS_IOC_DE/COMPRESS_FILE are allowed unexpectly,
> which could crash that file.
> To fix it, let's do not allow F2FS_IOC_DE/COMPRESS_IOCTL if a file already
> has FI_COMPRESS_RELEASED flag.
> 
> This is the reproduction process:
> 1. $ chattr +c ./file
> 2. $ dd if=/dev/zero of=./file bs=4096 count=2000 oflag=append
> conv=notrunc 3. $ sync
> 4. $ do_compress ./file      ; call F2FS_IOC_COMPRESS_FILE
> 5. $ get_compr_blocks ./file ; call F2FS_IOC_GET_COMPRESS_BLOCKS

Oops! Do we need to call F2FS_IOC_RELEASE_COMPRESS_BLOCKS here?
Maybe, you need to revise reproduction process and to make v2 patch.

> 6. $ do_compress ./file      ; call F2FS_IOC_COMPRESS_FILE again
> 7. $ get_compr_blocks ./file ; call F2FS_IOC_GET_COMPRESS_BLOCKS again
> 
> You can find compr_blocks has a negative value.
> 
> Fixes: 5fdb322ff2c2b ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and
> F2FS_IOC_COMPRESS_FILE")
> 
> Signed-off-by: Junbeom Yeom <junbeom.yeom@samsung.com>
> Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
> Signed-off-by: Youngjin Gil <youngjin.gil@samsung.com>
> Signed-off-by: Jaewook Kim <jw5454.kim@samsung.com>
> ---
>  fs/f2fs/file.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index
> 6b1b030830ca..a4713b7e12cb 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -3945,6 +3945,11 @@ static int f2fs_ioc_decompress_file(struct file
> *filp, unsigned long arg)
>  		goto out;
>  	}
> 
> +	if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
>  	ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
>  	if (ret)
>  		goto out;
> @@ -4012,6 +4017,11 @@ static int f2fs_ioc_compress_file(struct file *filp,
> unsigned long arg)
>  		goto out;
>  	}
> 
> +	if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
>  	ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
>  	if (ret)
>  		goto out;
> --
> 2.17.1