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

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Date:	Sun, 15 Nov 2015 12:05:45 +0100
From:	Vegard Nossum <vegard.nossum@...cle.com>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Richard Weinberger <richard@....at>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Endless getdents() in vfat filesystem

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.
"""

Thanks,


Vegard
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