linux-kernel - Re: [PATCH v2] f2fs: do not allow to decompress files have FI_COMPRESS

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Date:   Thu, 4 Aug 2022 21:32:54 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaewook Kim <jw5454.kim@...sung.com>, jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, sj1557.seo@...sung.com,
        junbeom.yeom@...sung.com, youngjin.gil@...sung.com
Subject: Re: [PATCH v2] f2fs: do not allow to decompress files have
 FI_COMPRESS_RELEASED

On 2022/8/3 16:53, Jaewook Kim wrote:
> 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.  $ touch ./file
> 2.  $ chattr +c ./file
> 3.  $ dd if=/dev/random of=./file bs=4096 count=30 conv=notrunc
> 4.  $ dd if=/dev/zero of=./file bs=4096 count=34 seek=30 conv=notrunc
> 5.  $ sync
> 6.  $ do_compress ./file      ; call F2FS_IOC_COMPRESS_FILE
> 7.  $ get_compr_blocks ./file ; call F2FS_IOC_GET_COMPRESS_BLOCKS
> 8.  $ release ./file          ; call F2FS_IOC_RELEASE_COMPRESS_BLOCKS
> 9.  $ do_compress ./file      ; call F2FS_IOC_COMPRESS_FILE again
> 10. $ get_compr_blocks ./file ; call F2FS_IOC_GET_COMPRESS_BLOCKS again
> 
> This reproduction process is tested in 128kb cluster size.
> 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@...sung.com>
> Signed-off-by: Sungjong Seo <sj1557.seo@...sung.com>
> Signed-off-by: Youngjin Gil <youngjin.gil@...sung.com>
> Signed-off-by: Jaewook Kim <jw5454.kim@...sung.com>

Reviewed-by: Chao Yu <chao@...nel.org>

Thanks,