lkml.org 
[lkml]   [2013]   [Aug]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch] xfs: check for underflow in xfs_iformat_fork()
Dan,

On Fri, Aug 16, 2013 at 08:26:50AM +1000, Dave Chinner wrote:
> On Thu, Aug 15, 2013 at 09:37:06AM -0500, Ben Myers wrote:
> > Hey Dan & Jeff,
> >
> > On Thu, Aug 15, 2013 at 06:10:43PM +0800, Jeff Liu wrote:
> > > On 08/15/2013 01:53 PM, Dan Carpenter wrote:
> > >
> > > > The "di_size" variable comes from the disk and it's a signed 64 bit.
> > > > We check the upper limit but we should check for negative numbers as
> > > > well.
> > > >
> > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > > >
> > > > diff --git a/fs/xfs/xfs_inode_fork.c b/fs/xfs/xfs_inode_fork.c
> > > > index 123971b..849fc70 100644
> > > > --- a/fs/xfs/xfs_inode_fork.c
> > > > +++ b/fs/xfs/xfs_inode_fork.c
> > > > @@ -167,7 +167,8 @@ xfs_iformat_fork(
> > > > }
> > > >
> > > > di_size = be64_to_cpu(dip->di_size);
> > > > - if (unlikely(di_size > XFS_DFORK_DSIZE(dip, ip->i_mount))) {
> > > > + if (unlikely(di_size < 0 ||
> > >
> > > But the di_size is initialized to ZERO while allocating a new inode on disk.
> > > I wonder if that is better to ASSERT in this case because the current check
> > > is used to make sure that the item is inlined, or we don't need it at all.
> >
> > Hmm. Dan's additional check looks good to me. In this case I'd say the forced
> > shutdown is more appropriate than an assert, because here we're reading the
> > inode from disk, as opposed to looking at a structure that is already incore
> > which we think we've initialized. We want to handle unexpected inputs from
> > disk without crashing even if we are CONFIG_XFS_DEBUG.
>
> There are lots of places where we only check di_size to be greater
> than some value, and don't check for it being less than zero. Hence
> I think that a better solution might be to di_size unsigned as that
> will catch "negative" sizes for all types of situations.

What do you say to making di_size unsigned? Any interest?

Thanks,
Ben


\
 
 \ /
  Last update: 2013-08-23 19:41    [W:1.557 / U:0.320 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site