linux-kernel - Re: [PATCH] staging: erofs: harden inode lookup for 32-bit platforms

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Message-ID: <b6baf932-64e5-c902-7e7f-02094b96a8d6@huawei.com>
Date:   Thu, 11 Oct 2018 17:46:26 +0800
From:   Gao Xiang <gaoxiang25@...wei.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <devel@...verdev.osuosl.org>, <linux-erofs@...ts.ozlabs.org>,
        Chao Yu <yuchao0@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>, <weidu.du@...wei.com>,
        Miao Xie <miaoxie@...wei.com>
Subject: Re: [PATCH] staging: erofs: harden inode lookup for 32-bit platforms



On 2018/10/11 16:44, Dan Carpenter wrote:
> On Tue, Oct 09, 2018 at 10:07:13PM +0800, Gao Xiang wrote:
>> This patch introduces inode hash function, test and set callbacks,
>> and iget5_locked to find the right inode for 32-bit platforms.
>>
> 
> The way I read this changelog, we're trying to deal with corrupt file
> systems?  Is that correct?  Presumably in the current code it could lead
> to a Oops or something?

No, this commit isn't trying to deal with corrupt file systems.
In EROFS, the nid is not continuous and it represents the inode offset
inode offset = nid * 32.
Therefore the nid is 64-bit both for 32-bit and 64-bit platforms. However,
i_ino is 'unsigned long', which means for 32-bit platforms, i_ino is not enough
to contain the nid.

Therefore, we should use iget5_locked for this case.

> 
> regards,
> dan carpenter
>