linux-kernel - Re: [PATCH] reiserfs: fix broken xattr handling (heap corruption, bad retval)

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Date:   Mon, 13 Aug 2018 14:39:14 -0400
From:   Jeff Mahoney <jeffm@...e.com>
To:     Jann Horn <jannh@...gle.com>, Will Deacon <will.deacon@....com>
Cc:     reiserfs-devel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>, security@...nel.org,
        Al Viro <viro@...iv.linux.org.uk>,
        kernel list <linux-kernel@...r.kernel.org>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH] reiserfs: fix broken xattr handling (heap corruption, bad
 retval)

On 8/13/18 2:04 PM, Jann Horn wrote:
> On Mon, Aug 13, 2018 at 7:42 PM Will Deacon <will.deacon@....com> wrote:
>>
>> Hi Jann,
>>
>> On Fri, Aug 10, 2018 at 05:19:38AM +0200, Jann Horn wrote:
>>> On Thu, Aug 2, 2018 at 5:16 PM Jann Horn <jannh@...gle.com> wrote:
>>>>
>>>> This fixes the following issues:
>>>>
>>>>  - When a buffer size is supplied to reiserfs_listxattr() such that each
>>>>    individual name fits, but the concatenation of all names doesn't
>>>>    fit, reiserfs_listxattr() overflows the supplied buffer. This leads to
>>>>    a kernel heap overflow (verified using KASAN) followed by an
>>>>    out-of-bounds usercopy and is therefore a security bug.
>>>>  - When a buffer size is supplied to reiserfs_listxattr() such that a name
>>>>    doesn't fit, -ERANGE should be returned. But reiserfs instead just
>>>>    truncates the list of names; I have verified that if the only xattr on
>>>>    a file has a longer name than the supplied buffer length, listxattr()
>>>>    incorrectly returns zero.
>>>>
>>>> With my patch applied, -ERANGE is returned in both cases and the memory
>>>> corruption doesn't happen anymore.
>>>>
>>>> Credit for making me clean this code up a bit goes to Al Viro, who pointed
>>>> out that the ->actor calling convention is suboptimal and should be
>>>> changed.
>>>>
>>>> Fixes: 48b32a3553a5 ("reiserfs: use generic xattr handlers")
>>>> Cc: stable@...r.kernel.org
>>>> Signed-off-by: Jann Horn <jannh@...gle.com>
>>>
>>> +security@
>>> Ping. I have not received any replies to this patch, which fixes a
>>> kernel security bug, for a week.
>>> Whose tree should this go through? reiserfs is marked as "supported",
>>> but does not have a maintainer or a git repo listed, just a
>>> mailinglist, so I guess it probably has to go through either Al Viro's
>>> or akpm's tree? Looks like akpm signed off on the last commits in
>>> reiserfs...
>>
>> I think Andrew's tree makes the most sense for this,
> 
> Yeah, Andrew has already merged it. :)
> http://ozlabs.org/~akpm/mmots/broken-out/reiserfs-fix-broken-xattr-handling-heap-corruption-bad-retval.patch
> 
>> but perhaps we should
>> also patch MAINTAINERS so mark it as "Orphan"? Patch below.
> 
> Either that, or get someone to step up as maintainer? If I read
> https://marc.info/?l=reiserfs-devel&m=153214303506948&w=2#0 correctly,
> there's still an intent to fix things in reiserfs, even though no
> maintainer is listed. (Jeff Mahoney, who wrote that message and is
> CC'ed on this thread, seems to have been out of office last week - when
> I sent the "Ping" message a few days ago, I got a vacation
> autoresponder "I'll be out of the office until 13 August" from him.)

I suppose I can take a more active role here.  I'm probably the person
with the most experience with reiserfs who still has a role where I need
to care about it.

-Jeff

>> Will
>>
>> --->8
>>
>> From 07fbb021d5bbfe623fad10073b55704bda8e1f3d Mon Sep 17 00:00:00 2001
>> From: Will Deacon <will.deacon@....com>
>> Date: Mon, 13 Aug 2018 18:31:50 +0100
>> Subject: [PATCH] MAINTAINERS: Mark reiserfs as Orphan
>>
>> Reiserfs has no Maintainer and random fixes tend to be merged through
>> with Andrew or Al's tree. Demote the filesystem to "Orphan", since it's
>> clear no longer supported by anybody.
>>
>> Reported-by: Jann Horn <jannh@...gle.com>
>> Signed-off-by: Will Deacon <will.deacon@....com>
>> ---
>>  MAINTAINERS | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 544cac829cf4..b4fcc19cfb52 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -12077,7 +12077,7 @@ F:      include/linux/regmap.h
>>
>>  REISERFS FILE SYSTEM
>>  L:     reiserfs-devel@...r.kernel.org
>> -S:     Supported
>> +S:     Orphan
>>  F:     fs/reiserfs/
>>
>>  REMOTE PROCESSOR (REMOTEPROC) SUBSYSTEM
>> --
>> 2.1.4
> 

-- 
Jeff Mahoney
SUSE Labs




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