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

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Date:	Sat, 2 Nov 2013 08:44:46 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Chen Gang <gang.chen@...anux.com>
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 Sat, Nov 02, 2013 at 09:46:31PM +0800, Chen Gang wrote:
> On 11/01/2013 10:41 AM, Chen Gang wrote:
> > 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)".
> > 
> 
> Oh, for me, it is not suitable to move a file system sub-directory to
> "drivers/*/" sub-directory. And I can not find any sub-directory like
> 'staging' under "fs" sub-directory, either.
> 
> Do we have any sub-directory like "staging" in "fs" sub-directory? if
> no, do we have to create it or have to use another ways instead of?

Just move the filesystem to drivers/staging/befs.

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