Re: [PATCH] xfs: fix stack contents leakage in the v1 bulkstat/inumbers ioctls

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Jul 25, 2019 at 09:52:17AM +0300, Dan Carpenter wrote:
> On Wed, Jul 24, 2019 at 08:35:45AM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Explicitly initialize the onstack structures to zero so we don't leak
> > kernel memory into userspace when converting the in-core structure to
> > the v1 ioctl structure.
> > 
> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  fs/xfs/xfs_ioctl.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > index f193f7b288ca..44e1a290f053 100644
> > --- a/fs/xfs/xfs_ioctl.c
> > +++ b/fs/xfs/xfs_ioctl.c
> > @@ -719,7 +719,7 @@ xfs_fsbulkstat_one_fmt(
> >  	struct xfs_ibulk		*breq,
> >  	const struct xfs_bulkstat	*bstat)
> >  {
> > -	struct xfs_bstat		bs1;
> > +	struct xfs_bstat		bs1 = { 0 };
> 
> This sort of initialization is potentially problematic because some
> versions of GCC will change it as a series of assignments (which doesn't
> clear the struct hole).  It's not clear to me the rules where GCC does
> this and also I wish there were an option to disable that feature.

And poor maintainers like me didn't even /know/ that.... ok, I'll go
with an explicit memset like Eric suggested in the patch review.

--D

> [ I am still out of office until the end of the month ]
> 
> regards,
> dan carpenter
>