Re: [PATCH] xfs: check for negatives in xfs_exchange_range_checks()

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, May 06, 2024 at 11:40:25PM -0700, Christoph Hellwig wrote:
> On Tue, May 07, 2024 at 09:33:40AM +0300, Dan Carpenter wrote:
> > On Mon, May 06, 2024 at 11:06:17PM -0700, Christoph Hellwig wrote:
> > > On Sat, May 04, 2024 at 02:27:36PM +0300, Dan Carpenter wrote:
> > > > The fxr->file1_offset and fxr->file2_offset variables come from the user
> > > > in xfs_ioc_exchange_range().  They are size loff_t which is an s64.
> > > > Check the they aren't negative.
> > > > 
> > > > Fixes: 9a64d9b3109d ("xfs: introduce new file range exchange ioctl")
> > > 
> > > In this commit file1_offset and file2_offset are u64.  They used to
> > > be u64 in the initial submission, but we changed that as part of the
> > > review process.
> > 
> > I've just checked again, and I think it was loff_t in that commit.
> > There are two related structs, the one that's userspace API and the
> > one that's internal.  The userspace API is u64 but internally it's
> > loff_t.
> 
> Ah, yes.  The in-kernel ones probably just needs to move to use u64
> as well.

I don't think we want userspace to be able to exchangerange data at file
positions that they can't read or write with a standard fs syscall.

--D