linux-kernel - Re: [PATCH] xfs: check for negatives in xfs_exchange_range

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Date: Wed, 8 May 2024 12:20:22 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Dave Chinner <david@...morbit.com>
Cc: "Darrick J. Wong" <djwong@...nel.org>,
	Chandan Babu R <chandan.babu@...cle.com>, linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] xfs: check for negatives in xfs_exchange_range_checks()

On Wed, May 08, 2024 at 11:29:15AM +1000, Dave Chinner 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")
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> > ---
> > From static analysis.  Untested.  Sorry!
> > 
> >  fs/xfs/xfs_exchrange.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/fs/xfs/xfs_exchrange.c b/fs/xfs/xfs_exchrange.c
> > index c8a655c92c92..3465e152d928 100644
> > --- a/fs/xfs/xfs_exchrange.c
> > +++ b/fs/xfs/xfs_exchrange.c
> > @@ -337,6 +337,9 @@ xfs_exchange_range_checks(
> >  	if (IS_SWAPFILE(inode1) || IS_SWAPFILE(inode2))
> >  		return -ETXTBSY;
> >  
> > +	if (fxr->file1_offset < 0 || fxr->file2_offset < 0)
> > +		return -EINVAL;
> 
> Aren't the operational offset/lengths already checked for underflow
> and overflow via xfs_exchange_range_verify_area()?

Ah right.  Smatch complains in the middle of the two calls to
xfs_exchange_range_verify_area().  (It get's called in different places
depending on if the XFS_EXCHANGE_RANGE_TO_EOF flag is set).

regards,
dan carpenter