linux-kernel - Re: [PATCH] fs/befs/linuxvfs.c: need signed cast for variable 'block'

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Date:	Fri, 01 Nov 2013 10:41:25 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Kees Cook <keescook@...omium.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs/befs/linuxvfs.c: need signed cast for variable 'block'

On 11/01/2013 04:45 AM, Greg KH wrote:
> On Thu, Oct 31, 2013 at 12:08:33PM -0700, Kees Cook wrote:
>> On Thu, Oct 31, 2013 at 12:06 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>>> On Thu, Oct 31, 2013 at 09:53:59AM -0700, Kees Cook wrote:
>>>
>>>> If block (type sector_t) is unsigned, we shouldn't cast it signed.
>>>> This entire code path should be removed. What is BEFS's expected
>>>> maximum block size? (Looks like even befs_blocknr_t is u64, so nothing
>>>> seems trivially in danger of wrapping.) I would also note that all the
>>>> format strings are wrong too (%ld instead of %lu).
>>>
>>> FWIW, this
>>>         res = befs_fblock2brun(sb, ds, block, &run);
>>>         if (res != BEFS_OK) {
>>>                 befs_error(sb,
>>>                            "<--- befs_get_block() for inode %lu, block "
>>>                            "%ld ERROR", inode->i_ino, block);
>>>                 return -EFBIG;
>>>         }
>>> also looks wrong - ioctl(..., FIBMAP, ...) shouldn't be able to spew
>>> printks on a valid fs and hitting it with block number greater than
>>> file length will, AFAICS, trigger that.
>>>
>>> I agree that this code needs fixing, but just making gcc STFU about the
>>> comparison would only serve to hide the problem.  Anybody familiar with
>>> befs or willing to learn it?
>>
>> Agreed. MAINTAINERS shows it as orphaned. Perhaps it should be moved
>> into staging?
> 
> Only if we want to delete the thing.  I'll be glad to take it there, and
> remove it in 2 releases and then if anyone complains, we can add it back
> easily.  Just let me know.
> 

Excuse me, I am not quite familiar with BEFS, I guess your meaning is:

  "if it is no further more discussion (e.g. within 1 week, no members reply), you will remove it (take it to "drivers/staging" sub-directory)".

If what I guess is correct, I support you (else, please let me know)


Thanks.
-- 
Chen Gang
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