linux-kernel - Re: Endless getdents() in vfat filesystem

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Message-ID: <56486B59.9010400@nod.at>
Date:	Sun, 15 Nov 2015 12:24:09 +0100
From:	Richard Weinberger <richard@....at>
To:	Vegard Nossum <vegard.nossum@...cle.com>,
	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Endless getdents() in vfat filesystem

Am 15.11.2015 um 12:05 schrieb Vegard Nossum:
> On 11/14/2015 07:19 PM, OGAWA Hirofumi wrote:
>> Richard Weinberger <richard@....at> writes:
>>
>>>>> Yes, it does fixes the problem here, but I can't really comment on the
>>>>> correctness of the patch.
>>>>>
>>>>> Thanks for the quick reponse,
>>>>
>>>> I made cleanup and made sure fake_offset is corrected.
>>>>
>>>> Richard, Signed-off-by was missed in your patch, so I added. Can you
>>>> agree to Signed-off-by?
>>>
>>> Sure!
>>
>> Attached updated patch made smaller changes, and with missed Cc: stable.
>>
>> Andrew, please queue this up.
>>
>> Thanks.
>>
> 
> It would be nice to have a proper patch description too. How about this?
> 
> """
> For the root directory, . and .. are faked (using dir_emit_dots()) and
> ctx->pos is reset from 2 to 0.
> 
> A corrupted root directory could cause fat_get_entry() to fail, but
> ->iterate() (fat_readdir()) reports progress to the VFS (with ctx->pos
> rewound to 0), so any following calls to ->iterate() continue to return
> the same entries again and again.
> 
> The result is that userspace will never see the end of the directory,
> causing e.g. 'ls' to hang in a getdents() loop.
> """

Agreed. And you deserve also a Reported-and-tested-by. :-)

Thanks,
//richard
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