linux-kernel - Re: [RFC v3 36/45] NFSv4: Fix GETATTR bitmap verification

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 28 May 2015 16:50:00 -0400
From:	Trond Myklebust <trond.myklebust@...marydata.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Andreas Gruenbacher <andreas.gruenbacher@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>
Subject: Re: [RFC v3 36/45] NFSv4: Fix GETATTR bitmap verification

On Thu, May 28, 2015 at 4:33 PM, J. Bruce Fields <bfields@...ldses.org> wrote:
> On Fri, Apr 24, 2015 at 01:04:33PM +0200, Andreas Gruenbacher wrote:
>> The NFSv4 client sends the server GETATTR requests with different sets of
>> requested attributes depending on the situation.  The requested set of
>> attributes is encoded in a bitmap; the server replies with the set of
>> attributes it could return.  These bitmaps can be several words wide.  The
>> bitmap returned by the server is a subset of the bitmap sent by the client.
>>
>> While decoding the reply, the client tries to verify the reply bitmap: it
>> checks if any previous, unexpected attributes are left in the same word of the
>> bitmap for each attribute it tries to decode, then it clears the current
>> attribute's bit in the bitmap for the next decode function.
>>
>> The client fails to detect when unexpected attributes are sent after the last
>> expected attribute in each word in the bitmap.
>
> Is it important that the client catch that?

Right. What is the actual problem or bug that this patch is trying to
fix? Why do we care if a buggy server sends us extra info that we
didn't ask for?

Trond
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/