Dan, how are you running smatch?
I've been looking at smatch warnings/errors and don't get this error.
Do you have a custom smatch checker?
On Wed, Dec 4, 2024 at 2:50 PM Alex Markuze <amarkuze@xxxxxxxxxx> wrote:
>
> I assume a Coccinelle patch can be written, if one doesn't exist yet.
>
> On Tue, Dec 3, 2024 at 8:29 PM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> >
> > On Tue, Dec 03, 2024 at 11:06:50AM -0600, Alex Elder wrote:
> > > On 12/3/24 2:19 AM, Dan Carpenter wrote:
> > > > Hello Jeff Layton,
> > > >
> > > > Commit d48464878708 ("ceph: decode interval_sets for delegated inos")
> > > > from Nov 15, 2019 (linux-next), leads to the following Smatch static
> > > > checker warning:
> > > >
> > > > fs/ceph/mds_client.c:644 ceph_parse_deleg_inos()
> > > > warn: potential user controlled sizeof overflow 'sets * 2 * 8' '0-u32max * 8'
> > > >
> > > > fs/ceph/mds_client.c
> > > > 637 static int ceph_parse_deleg_inos(void **p, void *end,
> > > > 638 struct ceph_mds_session *s)
> > > > 639 {
> > > > 640 u32 sets;
> > > > 641
> > > > 642 ceph_decode_32_safe(p, end, sets, bad);
> > > > ^^^^
> > > > set to user data here.
> > > >
> > > > 643 if (sets)
> > > > --> 644 ceph_decode_skip_n(p, end, sets * 2 * sizeof(__le64), bad);
> > > > ^^^^^^^^^^^^^^^^^^^^^^^^^
> > > > This is safe on 64bit but on 32bit systems it can integer overflow/wrap.
> > >
> > > So the point of this is that "sets" is u32, and because that is
> > > multiplied by 16 when passed to ceph_decode_skip_n(), the result
> > > could exceed 32 bits? I.e., would this address it?
> > >
> > > if (sets) {
> > > size_t scale = 2 * sizeof(__le64);
> > >
> > > if (sets < SIZE_MAX / scale)
> > > ceph_decode_skip_n(p, end, sets * scale, bad);
> > > else
> > > goto bad;
> > > }
> > >
> >
> > Yes, that works. I don't know if there are any static checker warnings which
> > will complain that the "sets < SIZE_MAX / scale" is always true on 64 bit. I
> > don't think there is?
> >
> > regards,
> > dan carpenter
> >
> >
