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

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Message-ID: <CAFLxGvyzbMJA_=iy_=ZaQiJ_cqdRdiK-MF3rDYi=uaZ6fdWKHw@mail.gmail.com>
Date:	Sat, 14 Nov 2015 11:32:54 +0100
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Vegard Nossum <vegard.nossum@...cle.com>
Cc:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Endless getdents() in vfat filesystem

On Sat, Nov 14, 2015 at 2:19 AM, Vegard Nossum <vegard.nossum@...cle.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?

>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?

-- 
Thanks,
//richard

View attachment "__fat_readdir_cpos_fix.diff" of type "text/plain" (418 bytes)