linux-kernel - Re: [PATCH] ntfs: check for valid standard information attribute

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Message-ID: <A4498E63-33DC-4DAA-837D-D97B8F29F70C@tuxera.com>
Date:   Mon, 22 Feb 2021 14:18:50 +0000
From:   Anton Altaparmakov <anton@...era.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     "linux-ntfs-dev@...ts.sourceforge.net" 
        <linux-ntfs-dev@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Rustam Kovhaev <rkovhaev@...il.com>
Subject: Re: [PATCH] ntfs: check for valid standard information attribute

Hi Andrew,

Sorry for the delay in replying.

> On 19 Feb 2021, at 18:49, Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> On Fri, 19 Feb 2021 01:54:30 +0000 Anton Altaparmakov <anton@...era.com> wrote:
> 
>> Hi Andrew,
>> 
>> Can you please push this one upstream?  Thanks a lot in advance!
> 
> The changelog is a bit brief...

Yes you are right it is a bit brief.  I guess I thought the syzkaller link was sufficient...  Rustam would you like to resubmit with an improved/extended description?

>>> On 17 Feb 2021, at 15:59, Rustam Kovhaev <rkovhaev@...il.com> wrote:
>>> 
>>> we should check for valid STANDARD_INFORMATION attribute offset and
>>> length before trying to access it
> 
> It's a kernel a crash and I assume it results from mounting a corrupted
> filesystem?
> 
> I think it's worth a cc:stable, yes?

The problem is an invalid memory access due to corrupt on-disk metadata.

The issue with NTFS is that it is effectively a relational database so it is full of "struct X, field A" contains offset to "struct Y" so you get: "&struct Y = &struct X + X->A" and if the value of A is corrupt on-disk then your Y pointer is now pointing to random memory.

The patch fixes one such place by validating that Y pointer is within bounds of the structure/buffer it is in.

So I guess this could be worth a cc:stable?  I guess we can add it and Greg / others can decide whether to put it into stable or not...  Rustam when resubmitting with better description, please also add the "Cc: stable@...r.kernel.org" line together with the "Signed-off-by", etc lines (note no need to actually put this in CC: field of the email iteslf).

Best regards,

	Anton
-- 
Anton Altaparmakov <anton at tuxera.com> (replace at with @)
Lead in File System Development, Tuxera Inc., http://www.tuxera.com/
Linux NTFS maintainer