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

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Message-ID: <20131031204558.GA30290@kroah.com>
Date:	Thu, 31 Oct 2013 13:45:58 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Chen Gang <gang.chen@...anux.com>,
	"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 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.

thanks,

greg k-h
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