Re: [PATCH] NFSD: check for negative "len" values in nfssvc_decode_writeargs()

[Dan Carpenter <dan.carpenter@oracle.com>]

On Mon, Mar 14, 2022 at 05:42:58PM +0300, Chuck Lever III wrote:
> Hi Dan-
> 
> > On Mar 14, 2022, at 10:06 AM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> > 
> > This code checks the upper bound of "len" but it needs to check for
> > negative values as well.
> 
> It doesn't check because nfsd3_writeargs::len is a __u32,
> and the NFSv2 code here was copied from that assuming that
> nfsd_writeargs::len had the same signage. This is because...
> 
> https://datatracker.ietf.org/doc/html/rfc1832#section-3.13 says
> that the count field in a variable-length array is supposed to
> be unsigned.
> 
> Thus IMO nfsd_writeargs::len should be changed to __u32
> instead of adding the extra negativity check.
> 
> If you resend, make sure the format specifier in the dprintk()
> at the top of nfsd_proc_write() is adjusted accordingly.

Thanks for this tip.  It's weird that GCC doesn't complain if you don't
make this change to the printk.  :/

regards,
dan carpenter