Re: Endless getdents() in vfat filesystem

From	Richard Weinberger <richard@nod.at>
Newsgroups	linux.kernel
Subject	Re: Endless getdents() in vfat filesystem
Date	2015-11-14 16:10 +0100
Message-ID	<quKCJ-5Cl-5@gated-at.bofh.it> (permalink)
References	<quxPc-5G2-7@gated-at.bofh.it> <quGps-2Pe-7@gated-at.bofh.it> <quIrf-42Y-5@gated-at.bofh.it> <quKt4-5k2-3@gated-at.bofh.it>
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Am 14.11.2015 um 15:28 schrieb OGAWA Hirofumi:
> Vegard Nossum <vegard.nossum@oracle.com> writes:
> 
>> On 11/14/2015 11:32 AM, Richard Weinberger wrote:
>>> On Sat, Nov 14, 2015 at 2:19 AM, Vegard Nossum <vegard.nossum@oracle.com> wrote:
>>>> Hi,
>>>>
>>>> Using the attached disk image I observe that getdents() never returns
>>>> the end of the directory, i.e. mounting the disk image on a loopback
>>>> device and running 'ls' under strace shows an endless stream of:
>>>>
>>>> getdents(3, /* 2 entries */, 32768)     = 48
>>>> getdents(3, /* 2 entries */, 32768)     = 48
>>>> getdents(3, /* 2 entries */, 32768)     = 48
>>>> ...
>>>
>>> Please more details. Is this image hand crafted?
>>> If not, how has it been created? Is is supposed to work?
>>
>> It was created by fuzzing, it is not supposed to work per se.
>>
>>>  From a quick look it seems as the root directory is bad but we report
>>> progress in ->iterate.
>>> ctx->pos is 2, we set it back to 0, because of the faked dot entries.
>>> but fat_get_entry() did not make any progress and we report 0 back to VFS.
>>> So, VFS sees progress and the game continues.
>>>
>>> Does the attached patch help?
>>
>> 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!

Thanks,
//richard
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Thread

Endless getdents() in vfat filesystem Vegard Nossum <vegard.nossum@oracle.com> - 2015-11-14 02:30 +0100
  Re: Endless getdents() in vfat filesystem Richard Weinberger <richard.weinberger@gmail.com> - 2015-11-14 11:40 +0100
    Re: Endless getdents() in vfat filesystem Vegard Nossum <vegard.nossum@oracle.com> - 2015-11-14 13:50 +0100
      Re: Endless getdents() in vfat filesystem OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> - 2015-11-14 16:00 +0100
        Re: Endless getdents() in vfat filesystem Richard Weinberger <richard@nod.at> - 2015-11-14 16:10 +0100
          Re: Endless getdents() in vfat filesystem OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> - 2015-11-14 19:20 +0100
            Re: Endless getdents() in vfat filesystem Vegard Nossum <vegard.nossum@oracle.com> - 2015-11-15 12:10 +0100
              Re: Endless getdents() in vfat filesystem Richard Weinberger <richard@nod.at> - 2015-11-15 12:30 +0100
                Re: Endless getdents() in vfat filesystem OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> - 2015-11-15 14:00 +0100

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