linux-kernel - Re: [PATCH] erofs: fix to avoid infinite loop in z_erofs_do_read

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Date:   Mon, 10 Jul 2023 17:56:43 +0800
From:   Gao Xiang <hsiangkao@...ux.alibaba.com>
To:     Chunhai Guo <guochunhai@...o.com>, xiang@...nel.org
Cc:     chao@...nel.org, huyue2@...lpad.com, jefflexu@...ux.alibaba.com,
        linux-erofs@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] erofs: fix to avoid infinite loop in
 z_erofs_do_read_page() when read page beyond EOF



On 2023/7/10 17:34, Chunhai Guo wrote:
> z_erofs_do_read_page() may loop infinitely due to the inappropriate
> truncation in the below statement. Since the offset is 64 bits and min_t()
> truncates the result to 32 bits. The solution is to replace unsigned int
> with a 64-bit type, such as erofs_off_t.
>      cur = end - min_t(unsigned int, offset + end - map->m_la, end);
> 
>      - For example:
>          - offset = 0x400160000
>          - end = 0x370
>          - map->m_la = 0x160370
>          - offset + end - map->m_la = 0x400000000
>          - offset + end - map->m_la = 0x00000000 (truncated as unsigned int)
>      - Expected result:
>          - cur = 0
>      - Actual result:
>          - cur = 0x370
> 
> Signed-off-by: Chunhai Guo <guochunhai@...o.com>

I'd like to update the subject line manually to:

"erofs: avoid infinite loop in z_erofs_do_read_page() when reading beyond EOF"

since the original one is too long...

Otherwise it looks good to me,

Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
Reviewed-by: Gao Xiang <hsiangkao@...ux.alibaba.com>

Thanks,
Gao Xiang