linux-kernel - Re: [PATCH v2] z3fold: fix the potential encode bug in encod

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Message-ID: <CAMJBoFMcnH3ZPQpG=oAjD=K64O7MX_BdFvHvccvgCV4nFSfxXA@mail.gmail.com>
Date:   Mon, 17 Oct 2016 14:03:28 +0200
From:   Vitaly Wool <vitalywool@...il.com>
To:     zhong jiang <zhongjiang@...wei.com>
Cc:     Dave Chinner <david@...morbit.com>,
        Seth Jennings <sjenning@...hat.com>,
        Dan Streetman <ddstreet@...e.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH v2] z3fold: fix the potential encode bug in encod_handle

Hi Zhong Jiang,

On Mon, Oct 17, 2016 at 3:58 AM, zhong jiang <zhongjiang@...wei.com> wrote:
> Hi,  Vitaly
>
> About the following patch,  is it right?
>
> Thanks
> zhongjiang
> On 2016/10/13 12:02, zhongjiang wrote:
>> From: zhong jiang <zhongjiang@...wei.com>
>>
>> At present, zhdr->first_num plus bud can exceed the BUDDY_MASK
>> in encode_handle, it will lead to the the caller handle_to_buddy
>> return the error value.
>>
>> The patch fix the issue by changing the BUDDY_MASK to PAGE_MASK,
>> it will be consistent with handle_to_z3fold_header. At the same time,
>> change the BUDDY_MASK to PAGE_MASK in handle_to_buddy is better.

are you seeing problems with the existing code? first_num should wrap around
BUDDY_MASK and this should be ok because it is way bigger than the number
of buddies.

~vitaly